251
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Dalla Serra M, Bernhart I, Nordera P, Di Giorgio D, Ballio A, Menestrina G. Conductive properties and gating of channels formed by syringopeptin 25A, a bioactive lipodepsipeptide from Pseudomonas syringae pv. syringae, in planar lipid membranes. Mol Plant Microbe Interact 1999; 12:401-409. [PMID: 10226373 DOI: 10.1094/mpmi.1999.12.5.401] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Syringopeptin 25A, a pseudomonad lipodepsipeptide, can form ion channels in planar lipid membranes. Pore conductance is around 40 pS in 0.1 M NaCl. Channel opening is strongly voltage dependent and requires a negative potential on the same side of the membrane where the toxin was added. These pores open and close with a lifetime of several seconds. At negative voltages, an additional pore state of around 10 pS and a lifetime of around 30 ms is also present. The voltage dependence of the rates of opening and closing of the stable pores is exponential. This allows estimation of the equivalent charge that is moved across the membrane during the process of opening at about 2.6 elementary charges. When NaCl is present, the pore is roughly 3 times more permeant for anions than for cations. The current voltage characteristic of the pore is nonlinear, i.e., pore conductance is larger at negative than at positive voltages. The maximal conductance of the pore depends on the concentration of the salt present, in a way that varies almost linearly with the conductivity of the solution. From this, an estimate of a minimal pore radius of 0.4 nm was derived.
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Affiliation(s)
- M Dalla Serra
- CNR-ITC Centro Fisica Stati Aggregati, Povo, Trento, Italy
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252
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Dalla Serra M, Fagiuoli G, Nordera P, Bernhart I, Della Volpe C, Di Giorgio D, Ballio A, Menestrina G. The interaction of lipodepsipeptide toxins from Pseudomonas syringae pv. syringae with biological and model membranes: a comparison of syringotoxin, syringomycin, and two syringopeptins. Mol Plant Microbe Interact 1999; 12:391-400. [PMID: 10226372 DOI: 10.1094/mpmi.1999.12.5.391] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Pseudomonas syringae pv. syringae produces two groups of cyclic lipodepsipeptides (LDPs): the nona-peptides syringomycins, syringostatins, and syringotoxin (ST), and the more complex syringopeptins composed of either 22 or 25 amino acid residues (SP22 and SP25). Both classes of peptides significantly contribute to bacterial pathogenesis and their primary target of action seems to be the plasma membrane. We studied and compared the activity of some members of these two classes of LDPs on red blood cells and on model membranes (monolayers and unilamellar vesicles). All peptides induced red blood cell hemolysis. The mechanism was apparently that of a colloid-osmotic shock caused by the formation of pores, as it could be prevented by osmoticants of adequate size. Application of the Renkin equation indicated a radius of approximately 1 nm for the lesions formed by syringopeptins SP22A and SP25A, whereas those formed by syringomycin E (SRE) had a variable, dose-dependent size ranging from 0.7 up to 1.7 nm. All tested LDPs displayed surface activity, forming peptide monolayers with average molecular areas of 1.2 nm2 (SRE), 1.5 nm2 (SP22A), and 1.3 nm2 (SP25A). They also partitioned into preformed lipid monolayers occupying molecular areas that ranged from 0.6 to 1.7 nm2 depending on the peptide and the lipid composition of the film. These LDPs formed channels in lipid vesicles as indicated by the release of an entrapped fluorescent dye (calcein). The extent of permeabilization was dependent on the concentration of the peptide and the composition of the lipid vesicles, with a preference for those containing a sterol. From the dose dependence of the permeabilization it was inferred that LDPs increased membrane permeability by forming oligomeric channels containing from four to seven monomers. On average, syringopeptin oligomers were smaller than SRE and ST oligomers.
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Affiliation(s)
- M Dalla Serra
- CNR-ITC Centro Fisica Stati Aggregati, Povo, Trento, Italy
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253
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Gariani T, McBride JD, Leatherbarrow RJ. The role of the P2' position of Bowman-Birk proteinase inhibitor in the inhibition of trypsin. Studies on P2' variation in cyclic peptides encompassing the reactive site loop. Biochim Biophys Acta 1999; 1431:232-7. [PMID: 10209295 DOI: 10.1016/s0167-4838(99)00035-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The role of the P2' residue in proteinase inhibitors of the Bowman-Birk family was investigated using synthetic cyclic peptides based on the reactive site loop of the inhibitor. A series of 21 variants having different P2' residues was tested for inhibition of trypsin, and the rate at which they were hydrolysed by this enzyme was also measured. Variation at P2' was found to result in marked differences in inhibitory potency, with the best sequence (Ile) having a Ki value of 9 nM. Peptides with P2' Gly, Pro or Glu failed to demonstrate any measurable inhibition (Ki>1 mM). The peptides also displayed significant differences in the rates at which they were hydrolysed, which varied by over three orders of magnitude between the difference sequences. There was found to be overall correlation between the Ki value and the rate of hydrolysis, with peptides that inhibited best also being hydrolysed more slowly. The results are discussed in light of the sequence information for Bowman-Birk inhibitor proteins.
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Affiliation(s)
- T Gariani
- Department of Chemistry, Imperial College of Science, Technology and Medicine, South Kensington, London SW7 2AY, UK
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254
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Todt H, Dudley SC, Kyle JW, French RJ, Fozzard HA. Ultra-slow inactivation in mu1 Na+ channels is produced by a structural rearrangement of the outer vestibule. Biophys J 1999; 76:1335-45. [PMID: 10049317 PMCID: PMC1300113 DOI: 10.1016/s0006-3495(99)77296-6] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
While studying the adult rat skeletal muscle Na+ channel outer vestibule, we found that certain mutations of the lysine residue in the domain III P region at amino acid position 1237 of the alpha subunit, which is essential for the Na+ selectivity of the channel, produced substantial changes in the inactivation process. When skeletal muscle alpha subunits (micro1) with K1237 mutated to either serine (K1237S) or glutamic acid (K1237E) were expressed in Xenopus oocytes and depolarized for several minutes, the channels entered a state of inactivation from which recovery was very slow, i.e., the time constants of entry into and exit from this state were in the order of approximately 100 s. We refer to this process as "ultra-slow inactivation". By contrast, wild-type channels and channels with the charge-preserving mutation K1237R largely recovered within approximately 60 s, with only 20-30% of the current showing ultra-slow recovery. Coexpression of the rat brain beta1 subunit along with the K1237E alpha subunit tended to accelerate the faster components of recovery from inactivation, as has been reported previously of native channels, but had no effect on the mutation-induced ultra-slow inactivation. This implied that ultra-slow inactivation was a distinct process different from normal inactivation. Binding to the pore of a partially blocking peptide reduced the number of channels entering the ultra-slow inactivation state, possibly by interference with a structural rearrangement of the outer vestibule. Thus, ultra-slow inactivation, favored by charge-altering mutations at site 1237 in micro1 Na+ channels, may be analogous to C-type inactivation in Shaker K+ channels.
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Affiliation(s)
- H Todt
- Institute of Pharmacology of the University of Vienna, 1090 Vienna,
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255
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Abstract
Annetocin is a structurally and functionally oxytocin-related peptide isolated from the earthworm Eisenia foetida. We present the characterization of the annetocin cDNA. Sequence analyses of the deduced precursor polypeptide revealed that the annetocin precursor is composed of three segments: a signal peptide, an annetocin sequence flanked by a Gly C-terminal amidation signal and a Lys-Arg dibasic processing site, and a neurophysin domain, similar to other oxytocin family precursors. The proannetocin showed 37.4-45.8% amino acid homology to other prohormones. In the neurophysin domain, 14 cysteines and amino acid residues essential for association of a neurophysin with a vasopressin/oxytocin superfamily peptide were conserved, suggesting that the Eisenia neurophysin can bind to annetocin. Furthermore, in situ hybridization experiments demonstrated that the annetocin gene is expressed exclusively in neurons of the central nervous system predicted to be involved in regulation of reproductive behavior. These findings confirm that annetocin is a member of the vasopressin/oxytocin superfamily. This is the first identification of the cDNA encoding the precursor of an invertebrate oxytocin-related peptide and also the first report of the identification of an annelid vasopressin/oxytocin-related precursor.
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Affiliation(s)
- H Satake
- Suntory Institute for Bioorganic Research, Wakayamadai 1-1-1, Shimamoto-cho, Mishima-gun, Osaka 618-8503, Japan
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256
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Abstract
Seven novel macrocyclic polypeptides, designated as varv peptides B-H, have been isolated from the aerial parts of Viola arvensis. Their primary structures have been elucidated by automated Edman degradation and mass spectrometry. They all consist of 29 or 30 amino acid residues, covalently cyclized via the amide backbone and by three internal disulfide bridges. Their amino acid sequences are as follows: varv peptide B, cyclo-(TCFGGTCNTPGCSCDPWPMCSRNGLPVCGE); varv peptide C, cyclo-(TCVGGTCNTPGCSCSWPVCTRNGVPICGE); varv peptide D, cyclo-(TCVGGSCNTPGCSCSWPVCTRNGLPICGE); varv peptide E, cyclo-(TCVGGTCNTPGCSCSWPVCTRNGLPICGE); varv peptide F, cyclo-(TCTLGTCYTAGCSCSWPVCTRNGVPICGE); varv peptide G, cyclo-(TCFGGTCNTPGCSCDPWPVCSRNGVPVCGE); and varv peptide H, cyclo-(TCFGGTCNTPGCSCETWPVCSRNGLPVCGE). The varv peptides B-H exhibited high degrees of homology with the hitherto known macrocyclic peptides varv peptide A, kalata B1, violapeptide I, circulins A and B, and cyclopsychotride A.
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Affiliation(s)
- U Göransson
- Division of Pharmacognosy, Department of Pharmacy, Biomedical Center, Uppsala University, Box 579, S-751 23 Uppsala, Sweden
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257
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Minakata H, Ikeda T, Nagahama T, Oumi T, Ukena K, Matsushima O, Kawano T, Kimura Y. Comparison of precursor structures of the GGNG peptides derived from the earthworm Eisenia foetida and the leech Hirudo nipponia. Biosci Biotechnol Biochem 1999; 63:443-5. [PMID: 10192926 DOI: 10.1271/bbb.63.443] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Earthworm and leech cDNAs encoding the GGNG peptides, a family of myotropic peptides, were cloned and examined in this study. Both of the predicted precursor proteins are of polyprotein structure and contain several putative peptides distinct from the GGNG peptides. However, the precursors show organizations distinct from each other and no sequence similarity except for the GGNG peptides.
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Affiliation(s)
- H Minakata
- Suntory Institute for Bioorganic Research, Osaka, Japan
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258
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Konz D, Doekel S, Marahiel MA. Molecular and biochemical characterization of the protein template controlling biosynthesis of the lipopeptide lichenysin. J Bacteriol 1999; 181:133-40. [PMID: 9864322 PMCID: PMC103541 DOI: 10.1128/jb.181.1.133-140.1999] [Citation(s) in RCA: 119] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Lichenysins are surface-active lipopeptides with antibiotic properties produced nonribosomally by several strains of Bacillus licheniformis. Here, we report the cloning and sequencing of an entire 26.6-kb lichenysin biosynthesis operon from B. licheniformis ATCC 10716. Three large open reading frames coding for peptide synthetases, designated licA, licB (three modules each), and licC (one module), could be detected, followed by a gene, licTE, coding for a thioesterase-like protein. The domain structure of the seven identified modules, which resembles that of the surfactin synthetases SrfA-A to -C, showed two epimerization domains attached to the third and sixth modules. The substrate specificity of the first, fifth, and seventh recombinant adenylation domains of LicA to -C (cloned and expressed in Escherichia coli) was determined to be Gln, Asp, and Ile (with minor Val and Leu substitutions), respectively. Therefore, we suppose that the identified biosynthesis operon is responsible for the production of a lichenysin variant with the primary amino acid sequence L-Gln-L-Leu-D-Leu-L-Val-L-Asp-D-Leu-L-Ile, with minor Leu and Val substitutions at the seventh position.
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Affiliation(s)
- D Konz
- Philipps-Universität Marburg, Fachbereich Chemie/Biochemie, 35032 Marburg, Germany
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259
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Abstract
Embryonic and larval expression patterns of the sericin-1 gene and its presumed transcription factor, SGF-3/POU-M1, in the silk gland were analyzed by in situ hybridization and immunohistochemistry. The sericin-1 transcripts were first detected at embryonic stage 26 in an increasing gradient pattern in the middle and posterior part of the middle silk gland (MSG), while at the same stage the SGF-3/POU-M1 was already present in the entire anterior silk gland (ASG) and in the MSG but with a decreasing gradient pattern. The latter expression pattern was consistently maintained through all larval stages, while the sericin-1 expression was detected during the feeding stages but disappeared at the molting stages. These observations suggest that, although the SGF-3/POU-M1 was proposed to be a positive transcription factor for the sericin-1 gene, the protein might function in a negative manner on sericin-1 gene transcription. Alternatively, it is also possible that the sericin-1 gene might require another unidentified factor or mediator for in vivo transcription.
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Affiliation(s)
- K Matsunami
- Graduate University for Advanced Studies, Okazaki, Japan
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260
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Iverson GM, Jones DS, Marquis D, Linnik MD, Victoria EJ. A chemically defined, toleragen-based approach for targeting anti-beta2-glycoprotein I antibodies. Lupus 1998; 7 Suppl 2:S166-9. [PMID: 9814697 DOI: 10.1177/096120339800700236] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Antiphospholipid syndrome is characterized by a prothrombotic state and the presence of beta2-glycoprotein I (beta2-GPI)-dependent antiphospholipid antibodies. The feasibility of a B cell tolerance-based approach for specific reduction of anti-beta2-GPI antibodies was investigated. Anti-beta2-GPI antibodies isolated from a patient with antiphospholipid syndrome were used to screen peptide libraries expressed in phage, resulting in the identification of a phage that specifically bound anti-beta2-GPI antibodies. The phage-displayed peptide was identified and chemically optimized to generate a synthetic 14-mer peptide with an internal thioether linkage (LJP 685) that retained the binding profile of the original phage. LJP 685 was conjugated to a defined, non-immunogenic organic platform to generate a tetravalent presentation of LJP 685 for use as a toleragen. Tetravalent LJP 685 induced a dose-dependent reduction in antibody levels in mice previously immunized and boosted with LJP 685 coupled to the carrier keyhole limpet hemocyanin. These experiments support the technical feasibility of a tolerance-based approach for reducing anti-beta2-GPI antibodies in vivo.
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Affiliation(s)
- G M Iverson
- La Jolla Pharmaceutical Company, San Diego, CA 92121, USA
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261
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Yu S, Fiss E, Jacobs WR. Analysis of the exochelin locus in Mycobacterium smegmatis: biosynthesis genes have homology with genes of the peptide synthetase family. J Bacteriol 1998; 180:4676-85. [PMID: 9721311 PMCID: PMC107483 DOI: 10.1128/jb.180.17.4676-4685.1998] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/1998] [Accepted: 06/29/1998] [Indexed: 11/20/2022] Open
Abstract
Mycobacteria secrete the siderophore exochelin when grown under iron-limiting conditions. In order to understand iron uptake mechanisms in mycobacteria, we have taken a genetic approach to identify those genes involved in exochelin biosynthesis and transport in Mycobacterium smegmatis. Of the 6,000 chemically mutagenized clones of M. smegmatis mc2155 screened on agar plates containing chrome azural S, 19 mutants that had lost the ability to produce or secrete exochelin were identified. Thirteen of these mutants were complemented by a single M. smegmatis cosmid. Sequence analysis of this cosmid revealed nine open reading frames, three of which are homologous to genes encoding transporter proteins, which are likely involved in exochelin transport. Complementation and Tn10 mutagenesis analysis identified two new genes, fxbB and fxbC, which are required for exochelin biosynthesis. The fxbB and fxbC genes encode large proteins of 257 and 497 kDa, respectively, which are highly homologous to peptide synthetases, indicating that exochelin biosynthesis occurs by a nonribosomal mechanism.
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Affiliation(s)
- S Yu
- Howard Hughes Medical Institute, Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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262
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Yakimov MM, Kröger A, Slepak TN, Giuliano L, Timmis KN, Golyshin PN. A putative lichenysin A synthetase operon in Bacillus licheniformis: initial characterization. Biochim Biophys Acta 1998; 1399:141-53. [PMID: 9765590 DOI: 10.1016/s0167-4781(98)00096-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Certain Bacillus licheniformis strains isolated from oil wells have been shown to produce a very effective biosurfactant, lichenysin A, which is structurally similar to another less active lipopeptide, surfactin. Surfactin, like many small peptides in prokaryotes and lower eukaryotes, is synthesized non-ribosomally by multi-enzyme peptide synthetase complex. Analysis of several peptide synthetases of bacterial and fungal origin has revealed a high degree of sequence conservation. Two 35-mer oligonucleotides derived from highly conserved motifs ('core I' and 'core II') of surfactin synthetase were used to identify the cloned putative operon of lichenysin A synthetase lchA from B. licheniformis BNP29, a strain not amenable to genetic manipulation in a BAC system (F-plasmid-based bacterial artificial chromosome) based on Escherichia coli and its single-copy plasmid F-factor. A 32.4 kb fragment containing lichenysin A biosynthesis locus was sequenced and analysed. The structural architecture of putative lichenysin A synthetase protein containing seven amino acid (aa) activation-thiolation, two epimerization and one thioesterase domains is discussed in terms of its similarity to surfactin and other peptide synthetases. The 100 aa peptide chain situated between the highly conserved signature sequences FDXX and NXYGPTE(IV)X within amino acid binding domains of peptide synthetases is proposed to be a minimal block dictating the substrate specificity of the enzymes. A new operon-type structure has been localized directly upstream from the lichenysin A synthetase genes which, on the basis of sequence determination, potentially encode a four-member ABC-type transport system involved in product secretion.
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Affiliation(s)
- M M Yakimov
- Department of Microbiology, GBF National Research Centre for Biotechnology, Braunschweig, Germany.
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263
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Zhu W, Arceneaux JE, Beggs ML, Byers BR, Eisenach KD, Lundrigan MD. Exochelin genes in Mycobacterium smegmatis: identification of an ABC transporter and two non-ribosomal peptide synthetase genes. Mol Microbiol 1998; 29:629-39. [PMID: 9720878 DOI: 10.1046/j.1365-2958.1998.00961.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Many strains of mycobacteria produce two ferric chelating substances that are termed exochelin (an excreted product) and mycobactin (a cell-associated product). These agents may function as iron acquisition siderophores. To examine the genetics of the iron acquisition system in mycobacteria, ultraviolet (UV) and transposon (Tn611) mutagenesis techniques were used to generate exochelin-deficient mutants of Mycobacterium smegmatis strains ATCC 607 and LR222 respectively. Mutants were identified on CAS siderophore detection agar plates. Comparisons of the amounts of CAS-reactive material excreted by the possible mutant strains with that of the wild-type strains verified that seven UV mutant strains and two confirmed transposition mutant strains were deficient in exochelin production. Cell-associated mycobactin production in the mutants appeared to be normal. From the two transposon mutants, the mutated gene regions were cloned and identified by colony hybridization with an IS6100 probe, and the DNA regions flanking the transposon insertion sites were then used as probes to clone the wild-type loci from M. smegmatis LR222 genomic DNA. Complementation assays showed that an 8 kb PstI fragment and a 4.8 kb PstI/SacI subclone of this fragment complemented one transposon mutant (LUN2) and one UV mutant (R92). A 10.1 kb SacI fragment restored exochelin production to the other transposon mutant (LUN1). The nucleotide sequence of the 15.3 kb DNA region that spanned the two transposon insertion sites overlapped the 5' region of the previously reported exochelin biosynthetic gene fxbA and contained three open reading frames that were transcribed in the opposite orientation to fxbA. The corresponding genes were designated exiT, fxbB and fxbC. The deduced amino acid sequence of ExiT suggested that it was a member of the ABC transporter superfamily, while FxbB and FxbC displayed significant homology with many enzymes (including pristinamycin I synthetase) that catalyse non-ribosomal peptide synthesis. We propose that the peptide backbone of the siderophore exochelin is synthesized in part by enzymes resembling non-ribosomal peptide synthetases and that the ABC transporter ExiT is responsible for exochelin excretion.
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Affiliation(s)
- W Zhu
- Department of Microbiology, University of Mississippi Medical Center, Jackson 39216, USA
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264
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Shon KJ, Olivera BM, Watkins M, Jacobsen RB, Gray WR, Floresca CZ, Cruz LJ, Hillyard DR, Brink A, Terlau H, Yoshikami D. mu-Conotoxin PIIIA, a new peptide for discriminating among tetrodotoxin-sensitive Na channel subtypes. J Neurosci 1998; 18:4473-81. [PMID: 9614224 PMCID: PMC6792697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
We report the characterization of a new sodium channel blocker, mu-conotoxin PIIIA(mu-PIIIA). The peptide has been synthesized chemically and its disulfide bridging pattern determined. The structure of the new peptide is: [sequence: see text] where Z = pyroglutamate and O = 4-trans-hydroxyproline. We demonstrate that Arginine-14 (Arg14) is a key residue; substitution by alanine significantly decreases affinity and results in a toxin unable to block channel conductance completely. Thus, like all toxins that block at Site I, mu-PIIIA has a critical guanidinium group. This peptide is of exceptional interest because, unlike the previously characterized mu-conotoxin GIIIA (mu-GIIIA), it irreversibly blocks amphibian muscle Na channels, providing a useful tool for synaptic electrophysiology. Furthermore, the discovery of mu-PIIIA permits the resolution of tetrodotoxin-sensitive sodium channels into three categories: (1) sensitive to mu-PIIIA and mu-conotoxin GIIIA, (2) sensitive to mu-PIIIA but not to mu-GIIIA, and (3) resistant to mu-PIIIA and mu-GIIIA (examples in each category are skeletal muscle, rat brain Type II, and many mammalian CNS subtypes, respectively). Thus, mu-conotoxin PIIIA provides a key for further discriminating pharmacologically among different sodium channel subtypes.
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Affiliation(s)
- K J Shon
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio 44106, USA
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265
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Kaga A, Ishimoto M. Genetic localization of a bruchid resistance gene and its relationship to insecticidal cyclopeptide alkaloids, the vignatic acids, in mungbean (Vigna radiata L. Wilczek). Mol Gen Genet 1998; 258:378-84. [PMID: 9648742 DOI: 10.1007/s004380050744] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Bruchid resistance, controlled by a single dominant gene (Br) in a wild mungbean accession (TC1966), has been incorporated into cultivated mungbean (Vigna radiata). The resistance gene simultaneously confers inhibitory activity against the bean bug, Riptortus clavatus Thunberg (Hemiptera: Alydidae). The resultant isogenic line (BC20 generation) was characterized by the presence of a group of novel cyclopeptide alkaloids, called vignatic acids. A linkage map was constructed for Br and the vignatic acid gene (Va) using restriction fragment length polymorphism (RFLP) markers and a segregating BC20F2 population. By screening resistant and susceptible parental lines with 479 primers, eight randomly amplified polymorphic DNA (RAPD) markers linked to Br were identified and cloned for use as RFLP probes. All eight RAPD-based markers, one mungbean, and four common bean genomic clones were effectively integrated around Br within a 3.7-cM interval. Br was mapped to a 0.7-cM segment between a cluster consisting of six markers and a common bean RFLP marker, Bng110. The six markers are closest to the bruchid resistance gene, approximately 0.2 cM away. The vignatic acid gene, Va, cosegregated with bruchid resistance. However, one individual was identified in the BC20F2 population that retained vignatic acids in spite of its bruchid susceptibility. Consequently, Va was mapped to a single locus at the same position as the cluster of markers and 0.2 cM away from Br. These results suggest that the vignatic acids are not the principal factors responsible for bruchid resistance in V. radiata but will facilitate the use of map-based cloning strategies to isolate the Br gene.
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Affiliation(s)
- A Kaga
- Legume Breeding Laboratory, National Agriculture Research Center, Tsukuba, Ibaraki, Japan
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266
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Sugiyama N, Marchot P, Kawanishi C, Osaka H, Molles B, Sine SM, Taylor P. Residues at the subunit interfaces of the nicotinic acetylcholine receptor that contribute to alpha-conotoxin M1 binding. Mol Pharmacol 1998; 53:787-94. [PMID: 9547372 DOI: 10.1124/mol.53.4.787] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The two binding sites in the pentameric nicotinic acetylcholine receptor of subunit composition alpha2 beta gamma delta are formed by nonequivalent alpha-gamma and alpha-delta subunit interfaces, which produce site selectivity in the binding of agonists and antagonists. We show by sedimentation analysis that 125I-alpha-conotoxin M1 binds with high affinity to the alpha-delta subunit dimers, but not to alpha-gamma dimers, nor to alpha, gamma, and delta monomers, a finding consistent with alpha-conotoxin M1 selectivity for the alpha delta interface in the intact receptor measured by competition against alpha-bungarotoxin binding. We also extend previous identification of alpha-conotoxin M1 determinants in the gamma and delta subunits to the alpha subunit interface by mutagenesis of conserved residues in the alpha subunit. Most mutations of the alpha subunit affect affinity similarly at the two sites, but Tyr93Phe, Val188Lys, Tyr190Thr, Tyr198Thr, and Asp152Asn affect affinity in a site-selective manner. Mutant cycle analysis reveals only weak or no interactions between mutant alpha and non-alpha subunits, indicating that side chains of the alpha subunit do not interact with those of the gamma or delta subunits in stabilizing alpha-conotoxin M1. The overall findings suggest different binding configurations of alpha-conotoxin M1 at the alpha-delta and alpha-gamma binding interfaces.
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Affiliation(s)
- N Sugiyama
- Department of Pharmacology, University of California, San Diego, La Jolla 92093, USA
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267
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Prachand MS, Dhingra MM, Saran A, Coutinho E, Bodi J, Süli-Vargha H, Medzihardszky K. Comparative conformational studies on cyclic hexapeptides corresponding to message sequence His-Phe-Arg-Trp of alpha-melanotropin by NMR. J Pept Res 1998; 51:251-65. [PMID: 9560000 DOI: 10.1111/j.1399-3011.1998.tb00422.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Solution conformation of cyclo(Gly1-His2-Phe3-Arg4-Trp5-Gly6) and its D-Phe analog corresponding to the message sequence [Gly-alpha-MSH5-10] of alpha-MSH has been studied by 1D and 2D proton magnetic resonance spectroscopy in dimethyl sulfoxide (DMSO)-d6 solution and in a DMSO-d6/H2O cryoprotective mixture. The NMR data for both the analogs in solution at 300 K cannot be interpreted based on a single ordered conformation, as evidenced by the broadening of only -NH resonances as well as the temperature coefficients of the amide protons. An analysis of the nuclear Overhauser effect (NOE) cross-peaks in conjunction with temperature coefficient data indicates an equilibrium of multiple conformers with a substantial population of particular conformational states at least in the D-analog. The molecular dynamics simulations without and with NOE constraints also reveal numerous low-energy conformers with two gamma-turns, a gamma-turn and a beta-turn, two beta-turns, etc. for both the analogs. The observed NMR spectra can be rationalized by a dynamic equilibrium of conformers characterized by a gamma-bend at Gly6, two gamma-bends at Phe3 and Gly6 and a conformer with a single beta-turn and a gamma-bend for the L-Phe analog. On the other hand, a conformation with two fused beta-turns around the two tetrads His2-D-Phe3-Arg4-Trp5 and Trp5-Gly6-Gly1-His2 dominates the equilibrium mixture for the D-Phe analog. For the D-Phe analog, the experimentally observed average conformation is corroborated by molecular dynamics simulations as well as by studies in cryoprotective solvent.
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Affiliation(s)
- M S Prachand
- Tata Institute of Fundamental Research, Mumbai, India
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268
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Chang NS, French RJ, Lipkind GM, Fozzard HA, Dudley S. Predominant interactions between mu-conotoxin Arg-13 and the skeletal muscle Na+ channel localized by mutant cycle analysis. Biochemistry 1998; 37:4407-19. [PMID: 9521760 DOI: 10.1021/bi9724927] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
High-affinity mu-conotoxin block of skeletal muscle Na+ channels depends on an arginine at position 13 (Arg-13). To understand both the mechanism of toxin interaction and the general structure of its binding site in the channel mouth, we examined by thermodynamic mutant cycle analysis the interaction between the critical Arg-13 and amino acid residues known to be in the channel's outer vestibule. Arg-13 interacts specifically with domain II Glu-758 with energy of about -3.0 kcal/mol, including both electrostatic and nonelectrostatic components, and with Glu-403 with energy of about -2.0 kcal/mol. Interactions with the other charged residues in the outer vestibule were shown to be almost entirely electrostatic, because these interactions were maintained when Arg-13 was replaced by lysine. These results place the bound Arg-13 at the channel mouth adjacent to the P (pore) loops of domains I and II. Distance estimates based on interaction energies suggest that the charged vestibule residues are in relative positions similar to those of the Lipkind-Fozzard vestibule model [Lipkind, G. M., and Fozzard, H. A. (1994) Biophys. J. 66, 1-13]. Kinetic analysis suggests that Arg-13 interactions are partially formed in the ligand-channel transition state.
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Affiliation(s)
- N S Chang
- Department of Anesthesia and Critical Care, The University of Chicago, Chicago, Illinois 60637, USA
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269
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Jacobsen R, Jimenez EC, Grilley M, Watkins M, Hillyard D, Cruz LJ, Olivera BM. The contryphans, a D-tryptophan-containing family of Conus peptides: interconversion between conformers. J Pept Res 1998; 51:173-9. [PMID: 9531419 DOI: 10.1111/j.1399-3011.1998.tb01213.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
We previously characterized contryphan-R, a D-tryptophan-containing octapeptide from the venom of Conus radiatus. In this study, we present evidence that the contryphan family of peptides is widely distributed in venoms of the fish-hunting cone snails. We purified, synthesized and characterized contryphan-Sm from Conus stercusmuscarum venom, and obtained molecular evidence for the existence of a third peptide, contryphan-P from Conus purpurascens venom ducts. The sequences of these three contryphans showed identity in seven of eight amino acids and a conserved pattern of post-translational modification. We also demonstrate that contryphan-Sm equilibrates between two distinct conformational states.
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Affiliation(s)
- R Jacobsen
- Department of Biology, University of Utah, Salt Lake City 84112, USA
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270
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Abstract
Over the past few years, evidence has accumulated that shows that circularly permuted proteins resulting from permutations in their coding genes can indeed occur naturally. In most instances, these circularly permuted amino acid sequences have been detected by sequence alignment of homologous proteins. Circular permutations may escape detection, however, when based on sequence comparisons alone, as recently illustrated by transaldolase, a member of the class I aldolase family.
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Affiliation(s)
- Y Lindqvist
- Department of Medical Biochemistry and Biophysics, Karolinska Institute, Stockholm, Sweden.
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271
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Garel A, Deleage G, Prudhomme JC. Structure and organization of the Bombyx mori sericin 1 gene and of the sericins 1 deduced from the sequence of the Ser 1B cDNA. Insect Biochem Mol Biol 1997; 27:469-477. [PMID: 9219370 DOI: 10.1016/s0965-1748(97)00022-2] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The sericin 1 primary transcript of the silkworm Bombyx mori is differentially spliced via a tissue- and developmentally-regulated process. From a middle silk gland cDNA library, we have elucidated the sequence of one of the four mRNAs, the 4.0 kb Ser1B mRNA. Determination of alternative or constitutive exons and intron-exon boundaries allowed us to establish the nine exon-eight intron structure of the Ser1 gene. From these and previous data, it was possible to deduce the sequence of the sericins 1 and to predict the secondary structure and physiochemical properties of the different regions of the proteins.
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Affiliation(s)
- A Garel
- Centre de Génétique Moléculaire et Cellulaire, U.M.R., Université C. Bernard, Lyon I, Villeurbanne, France
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272
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Abstract
Many thylakoid lumenal proteins are nuclear encoded, cytosolically synthesized, and reach their functional location after posttranslational targeting across two chloroplast envelope membranes and the thylakoid membrane via proteinaceous transport systems. To study whether these transmembrane transport machineries can translocate folded structures, we overexpressed the 17-kDa subunit of the oxygen-evolving complex of photosystem II (prOE17) that had been modified to contain a unique C-terminal cysteine. This allowed us to chemically link a terminal 6.5-kDa bovine pancreatic trypsin inhibitor (BPTI) moiety to prOE17 to create the chimeric protein prOE17-BPTI. Redox reagents and an irreversible sulfhydryl-specific cross-linker, bis-maleimidohexane, were used to manipulate the structure of BPTI. Import of prOE17-BPTI into isolated chloroplasts and thylakoids demonstrates that the small tightly folded BPTI domain is carried across both the chloroplast envelopes and the delta pH-dependent transmembrane transporter of the thylakoid membrane when linked to the correctly targeted OE17 precursor. Transport proceeded even when the BPTI moiety was internally cross-linked into a protease-resistant form. These data indicate that unfolding is not a ubiquitous requirement for protein translocation and that at least some domains of targeted proteins can maintain a nonlinear structure during their translocation into and within chloroplasts.
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Affiliation(s)
- S A Clark
- Division of Biological Sciences, University of California, Davis 95616, USA
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273
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Tossi A, Scocchi M, Zanetti M, Gennaro R, Storici P, Romeo D. An approach combining rapid cDNA amplification and chemical synthesis for the identification of novel, cathelicidin-derived, antimicrobial peptides. Methods Mol Biol 1997; 78:133-50. [PMID: 9276302 DOI: 10.1385/0-89603-408-9:133] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- A Tossi
- Department of Biochemistry, Biophysics, and Macromolecular Chemistry, University of Trieste, Italy
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274
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Schnapp D, Kemp GD, Smith VJ. Purification and Characterization of a Proline-Rich Antibacterial Peptide, with Sequence Similarity to Bactenecin-7, from the Haemocytes of the Shore Crab, Carcinus Maenas. ACTA ACUST UNITED AC 1996; 240:532-9. [PMID: 8856051 DOI: 10.1111/j.1432-1033.1996.0532h.x] [Citation(s) in RCA: 149] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Antibacterial peptides are important for non-specific host defence in many animals. They have been extensively characterized from mammals, amphibians, insects and chelicerates but have not so far been found in crustaceans. Here we report the presence of several constitutive antibacterial proteins, active against both gram-positive and gram-negative bacteria, in the haemocytes of the shore crab, Carcinus maenas. These proteins have molecular masses of > 70 kDa, approximately 45 kDa, approximately 14 kDa and 6.5 kDa. The 6.5 kDa peptide has been purified to homogeneity by Sep Pak C18 extraction, gel filtration and reverse-phase HPLC. Partial N-terminal sequence analysis further shows that it is proline rich and shares more than 60% identity in a 28-amino-acid overlap with the mature form of bactenecin 7, an antimicrobial peptide from bovine neutrophils which belongs to the cathelicidin family of mammalian peptide antibiotics.
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Affiliation(s)
- D Schnapp
- Gatty Marine Laboratory, School of Biological and Medical Sciences, University of St Andrews, Scotland
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275
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Rubio JP, Thompson JK, Cowman AF. The var genes of Plasmodium falciparum are located in the subtelomeric region of most chromosomes. EMBO J 1996; 15:4069-77. [PMID: 8670911 PMCID: PMC452127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
PfEMP1, a Plasmodium falciparum-encoded protein on the surface of infected erythrocytes is a ligand that mediates binding to receptors on endothelial cells. The PfEMP1 protein, which is encoded by the large var gene family, shows antigenic variation and changes in binding phenotype associated with alterations in antigenicity. We have constructed a yeast artificial chromosome contig of chromosome 12 from P. falciparum and show that var genes are arranged in four clusters; two lie amongst repetitive subtelomeric sequences and two occur in the more conserved central region. Analysis of parasite chromosomes by pulsed field gel electrophoresis (PFGE) demonstrates that most contain var genes and two-dimensional PFGE has shown that var genes are located at chromosome ends interspersed amongst repetitive sequences present in the subtelomeric complex. Analysis of a var gene located in the subtelomeric region of chromosome 12 has shown that it has close homologues at the opposite end of the chromosome and in the subtelomeric region of two other chromosomes. This suggests that recombination between heterologous chromosomes has occurred in the subtelomeric regions of these chromosomes. The subtelomeric location of var genes dispersed amongst repetitive sequences has important implications for generation of antigenic variants and novel cytoadherent specificities of this protein.
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Affiliation(s)
- J P Rubio
- The Walter and Eliza Hall Institute of Medical Research, Royal Melbourne Hospital, Melbourne, Victoria, Australia 3050
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276
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Abstract
To isolate peptide ligands that bound calmodulin (CaM) specifically, we screened an M13 phage library displaying cyclized octamer random peptides with immobilized bovine CaM. Isolates were recovered, sequenced, and deduced to express nine independent peptides, five of which contained the sequence Trp-Gly-Lys (WGK). Four of the nine peptide sequences were synthesized in cyclized, biotinylated form. All of the peptides required Ca2+ to bind CaM. The cyclized, disulfide-bonded form of one such peptide, SCLRWGKWSNCGS, bound CaM better than its reduced form or an analogue in which the cysteine residues were replaced by serine. The cyclized peptide also exhibited the ability to inhibit CaM-dependent kinase activity. Systematic alanine substitution of residues in this peptide sequence implicate the tryptophan residue as being critical for binding, with other residues contributing to binding to varying degrees. Cloning of ligand targets (COLT) confirmed the specificity of one of the cyclized peptides, yielding full-length and C-terminal CaM clones, in addition to a full-length clone of troponin C, a CaM-related protein. This study has demonstrated that conformationally constrained peptides isolated from a phage library acted as specific, Ca(2+)-dependent CaM ligands.
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Affiliation(s)
- H H Pierce
- Department of Biology, University of North Carolina at Chapel Hill 27599, USA
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277
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Suzuki Y, Kokubo H, Ohno K. [Developmental expression patterns and target assignment of the bombyx fork head and POU-M1 genes]. Tanpakushitsu Kakusan Koso 1996; 41:1083-1087. [PMID: 8741629] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Affiliation(s)
- Y Suzuki
- Okazaki National Research Institutes, National Institute for Basic Biology, Japan
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278
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Pitkin JW, Panaccione DG, Walton JD. A putative cyclic peptide efflux pump encoded by the TOXA gene of the plant-pathogenic fungus Cochliobolus carbonum. Microbiology (Reading) 1996; 142 ( Pt 6):1557-1565. [PMID: 8704997 DOI: 10.1099/13500872-142-6-1557] [Citation(s) in RCA: 197] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Race 1 isolates of Cochliobolus carbonum are pathogenic on certain maize lines due to production of a host-selective cyclic tetrapeptide, HC-toxin. Flanking HTS1, which encodes the central enzyme in HC-toxin biosynthesis, a gene was identified and named TOXA. Like HTS1, TOXA occurred only in isolates of the fungus that make HC-toxin and was present as two linked copies in most toxin-producing isolates. HTS1 and TOXA were transcribed in the opposite orientation and their transcriptional start sites were 386 bp apart. The predicted product of TOXA was a 58 kDa hydrophobic protein with 10-13 membrane-spanning regions. The sequence was highly similar to several members of the major facilitator superfamily that confer resistance to tetracycline, methylenomycin, and other antibiotics. Although it was possible to mutate one copy or the other of TOXA by targeted gene disruption, numerous attempts to disrupt both copies in a single strain were unsuccessful, suggesting that TOXA is an essential gene in strains that synthesize HC-toxin. On the basis of its presence only in HC-toxin-producing strains, its proximity to HTS1 and its predicted amino acid sequence, we propose that TOXA encodes an HC-toxin efflux pump which contributes to self-protection against HC-toxin and/or the secretion of HC-toxin into the extracellular milieu.
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Affiliation(s)
- John W Pitkin
- Department of Energy-Plant Research Laboratory, Michigan State University, East Lansing 48824, USA
| | - Daniel G Panaccione
- Department of Energy-Plant Research Laboratory, Michigan State University, East Lansing 48824, USA
| | - Jonathan D Walton
- Department of Energy-Plant Research Laboratory, Michigan State University, East Lansing 48824, USA
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279
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280
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Raj PA, Marcus E, Edgerton M. Delineation of an active fragment and poly(L-proline) II conformation for candidacidal activity of bactenecin 5. Biochemistry 1996; 35:4314-25. [PMID: 8605180 DOI: 10.1021/bi951681r] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Bactenecin 5 and its fragments [BN22 (1-22), BN16 (7-22), and BC24 (20-43)] were synthesized by solid-phase methods. Their antifungal activities on Candida albicans have been studied and compared with those of the native bactenecin 5. The conformational preferences of these peptides in aqueous and nonaqueous solutions and in lipid vesicles were examined by circular dichroism. The highly active N-terminal fragment (BN16) was examined in aqueous solution using 500 MHz two-dimensional NMR. Bactenecin 5 and its fragments are potent candidacidal agents against C. albicans. The N-terminal fragments (BN22 and BN16) of bactenecin 5 are relatively more active than the C-terminal fragment BC24, especially at lower concentrations. The N-terminal region (7-22) which retains the activity of the whole molecule appears to be the functional domain for candidacidal activity. The CD spectra of bactenecin 5 and its fragments are reminiscent of the CD spectrum of poly(L-proline) type II structure in aqueous and nonaqueous solutions and also in lipid vesicles. The temperature dependence of NH chemical shifts and 1H/2H exchange effect on amide resonances suggest the absence of intramolecularly hydrogen-bonded NH groups. The coupling constant (JNH-CalphaH) values, conformational restriction offered by the Pro residues (phi = -60 degrees +/- 15 degrees), the set of medium- and short-range nuclear Overhauser effects observed for the active N-terminal fragment (BN16), and the restrained structure calculation using DIANA suggest that poly(L-proline) type II conformers of the peptide molecules could be significantly populated in aqueous solution. The ability of bactenecin peptides to induce disruption of lipid vesicles correlates well with their activity. Our results suggest that poly(L-proline) type II structure may, indeed, be the biologically active conformation for candidacidal activity of bactenecin peptides.
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Affiliation(s)
- P A Raj
- Department of Oral Biology, State University of New York at Buffalo, 14214, USA
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281
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Abstract
Genetically encoded libraries of peptides and oligonucleotides are well suited for the identification of ligands for many macromolecules. A major drawback of these techniques is that the resultant ligands are subject to degradation by naturally occurring enzymes. Here, a method is described that uses a biologically encoded library for the identification of D-peptide ligands, which should be resistant to proteolytic degradation. In this approach, a protein is synthesized in the D-amino acid configuration and used to select peptides from a phage display library expressing random L-amino acid peptides. For reasons of symmetry, the mirror images of these phage-displayed peptides interact with the target protein of the natural handedness. The value of this approach was demonstrated by the identification of a cyclic D-peptide that interacts with the Src homology 3 domain of c- SRC. Nuclear magnetic resonance studies indicate that the binding site for this D-peptide partially overlaps the site for the physiological ligands of this domain.
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Affiliation(s)
- T N Schumacher
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge MA 02142, USA
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282
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Giebel LB, Cass RT, Milligan DL, Young DC, Arze R, Johnson CR. Screening of cyclic peptide phage libraries identifies ligands that bind streptavidin with high affinities. Biochemistry 1995; 34:15430-5. [PMID: 7492543 DOI: 10.1021/bi00047a006] [Citation(s) in RCA: 172] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The screening of combinatorial peptide libraries has emerged as an important tool in the discovery of novel substrates or ligands for enzyme and receptor targets. For example, screening linear peptide libraries using streptavidin as a model receptor system has previously identified many low-affinity peptide ligands, all of which contain the common motif His-Pro-Gln (HPQ). We reasoned that constraining the conformational freedom of linear peptides by cyclization in a library would yield peptide ligands of increased affinity. Three different cyclic peptide libraries were constructed in an M13 phage display system as N-terminal pIII protein fusions. The random peptide sequences were flanked by two cysteine residues, which allows efficient disulfide bond formation and cyclization during phage assembly. These cyclic peptide libraries were screened with streptavidin as the model receptor system. Many sequences, all of which contained the motif His-Pro-Gln (HPQ), were discovered, and in the preceding paper, the structures of complexes of streptavidin-bound cyclic and linear peptides are described (Katz, 1995). Analysis of binding kinetics and affinities demonstrated that the conformationally constrained cyclic peptides bound streptavidin with affinities up to 3 orders of magnitude higher than linear peptides identified in previous library screens. These results demonstrate the potential of screening conformationally constrained peptide libraries for high-affinity novel receptor ligands or enzyme substrates.
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Affiliation(s)
- L B Giebel
- Department of Cytokine Biology, Arris Pharmaceutical Corporation, South San Francisco, California 94080, USA
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283
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Abstract
We describe a mutation in the outer vestibule region of the adult rat skeletal muscle voltage-gated Na+ channel (microliter) that dramatically alters binding of mu-conotoxin GIIIA (mu-CTX). Mutating the glutamate at position 758 to glutamine (E758Q) decreased mu-CTX binding affinity by 48-fold. Because the mutant channel showed both low tetrodotoxin (TTX) and mu-CTX affinities, these results suggested that mu-CTX bound to the outer vestibule and implied that the TTX- and mu-CTX-binding sites partially overlapped in this region. The mutation decreased the association rate of the toxin with little effect on the dissociation rate, suggesting that Glu-758 could be involved in electrostatic guidance of mu-CTX to its binding site. We propose a mechanism for mu-CTX block of the Na+ channel based on the analogy with saxitoxin (STX) and TTX, on the requirement of mu-CTX to have an arginine in position 13 to occlude the channel, and on this experimental result suggesting that mu-CTX binds in the outer vestibule. In this model, the guanidinium group of Arg-13 of the toxin interacts with two carboxyls known to be important for selectivity (Asp-400 and Glu-755), with the association rate of the toxin increased by interaction with Glu-758 of the channel.
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Affiliation(s)
- S C Dudley
- Department of Pharmacological and Physiological Sciences, University of Chicago, Illinois 60637, USA
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284
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Kleinkauf H, von Döhren H. The nonribosomal peptide biosynthetic system--on the origins of structural diversity of peptides, cyclopeptides and related compounds. Antonie Van Leeuwenhoek 1995; 67:229-42. [PMID: 7539997 DOI: 10.1007/bf00873687] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
A variety of peptides have been detected in microorganisms. Some have found applications in various fields, for example the classical beta-lactam antibiotics, immunosuppressors like cyclosporin, promising new antibacterials like teichoplanin or daptomycin and antifungals like echinocandin. For none of these has it been established how their complicated biosynthetic pathways have evolved or what functions they fulfill within or for their producers. So it is unclear what selection processes limit the range of their structural analogues within various groups of microorganisms. We here consider recent data in the field of biosynthesis and how they may suggest mechanisms of genetic diversity. These may illustrate the complexity of genetic and intracellular organization of biosynthetic pathways and indicate the cellular context of some metabolites related to the complex background of the production of each metabolite. Research focusing on various targets like the increase of productivity of fermentations or the spread of resistances to antibacterials is slowly being understood.
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Affiliation(s)
- H Kleinkauf
- Institute of Biochemistry and Molecular Biology, Technical University Berlin, Germany
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285
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Abstract
We describe a computer algorithm to predict native structures of proteins and peptides from their primary sequences, their known native radii of gyration, and their known disulfide bonding patterns, starting from random conformations. Proteins are represented as simplified real-space main chains with single-bead side chains. Nonlocal interactions are taken from structural database-derived statistical potentials, as in an earlier treatment. Local interactions are taken from simulations of (phi, psi) energy surfaces for each amino acid generated using the Biosym Discover program. Conformational searching is done by a genetic algorithm-based method. Reasonable structures are obtained for melittin (a 26-mer), avian pancreatic polypeptide inhibitor (a 36-mer), crambin (a 46-mer), apamin (an 18-mer), tachyplesin (a 17-mer), C-peptide of ribonuclease A (a 13-mer), and four different designed helical peptides. A hydrogen bond interaction was tested and found to be generally unnecessary for helical peptides, but it helps fold some sheet regions in these structures. For the few longer chains we tested, the method appears not to converge. In those cases, it appears to recover native-like secondary structures, but gets incorrect tertiary folds.
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Affiliation(s)
- S Sun
- Structural Biochemistry Program, Frederick Biomedical Supercomputing Center, National Cancer Institute, Frederick Cancer Research and Development Center, Maryland 21702, USA
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286
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Sine SM, Kreienkamp HJ, Bren N, Maeda R, Taylor P. Molecular dissection of subunit interfaces in the acetylcholine receptor: identification of determinants of alpha-conotoxin M1 selectivity. Neuron 1995; 15:205-11. [PMID: 7619523 DOI: 10.1016/0896-6273(95)90077-2] [Citation(s) in RCA: 147] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The acetylcholine receptor from vertebrate skeletal muscle is a pentamer of homologous subunits with composition alpha 2 beta gamma delta. Its two ligand binding sites, formed at alpha-gamma and alpha-delta interfaces, differ in their affinities for agonists and competitive antagonists, owing to different contributions of the gamma and delta subunits. To identify portions of the gamma and delta subunits that contribute to the binding sites, the experiments described here use gamma-delta subunit chimeras and site-specific mutants to determine the basis of the 10,000-fold selectivity of conotoxin M1 for the sites. Three distinct regions of the extracellular domain were found to contribute to conotoxin M1 selectivity, each containing a single residue responsible for the contribution of that region. Residues K34, S111, and F172 of the gamma subunit confer low affinity to the alpha-gamma binding site, whereas the corresponding residues of the delta subunit, S36, Y113, and I178, confer high affinity to the alpha-delta site. Identification of three separate determinants of ligand selectivity suggests a limited model of the folding pattern of the extracellular domain of the subunits.
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Affiliation(s)
- S M Sine
- Department of Physiology and Biophysics, Mayo Foundation, Rochester, Minnesota 55905, USA
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287
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Mach V, Takiya S, Ohno K, Handa H, Imai T, Suzuki Y. Silk gland factor-1 involved in the regulation of Bombyx sericin-1 gene contains fork head motif. J Biol Chem 1995; 270:9340-6. [PMID: 7721856 DOI: 10.1074/jbc.270.16.9340] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Silk gland factor-1 (SGF-1) regulates transcription of the Bombyx sericin-1 gene via interaction with the SA site. In this study, two related SGF-1 polypeptides of apparent molecular masses of 40 and 41 kDa were purified. Specific interaction of these proteins with the SA site was demonstrated by electrophoretic mobility shift and dimethyl sulfate methylation interference assays. The SGF-1 40-kDa protein was partially sequenced and characterized as a new member of the fork head/HNF-3 family. Several full-length cDNAs encoding the SGF-1 40-kDa and possibly also the 41-kDa proteins were cloned and sequenced. SGF-1 mRNA is expressed consistently with the presumed role of the SGF-1 protein product in regulating the sericin-1 gene. The SGF-1 protein contains putative transactivation domains. We conclude that the 40- and 41-kDa SGF-1 proteins affect transcription of the sericin-1 gene via binding to the SA site.
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Affiliation(s)
- V Mach
- National Institute for Basic Biology, Okazaki, Japan
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288
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Feignier C, Besson F, Michel G. Studies on lipopeptide biosynthesis by Bacillus subtilis: isolation and characterization of iturin-, surfactin+ mutants. FEMS Microbiol Lett 1995; 127:11-5. [PMID: 7737471 DOI: 10.1111/j.1574-6968.1995.tb07442.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Two mutant strains, M35 and M89, were obtained by UV irradiation from a wild-type Bacillus subtilis producing iturin and surfactin. Sporulation and surfactin production were similar in both mutants and in the parent strain, while the iturin production of M35 was 300-fold less than that of the wild-type strain; M89 did not produce any iturin. The analysis of the incorporation of sodium [1-14C]acetate into cellular lipids and lipopeptides showed that M89 still synthesized beta-amino fatty acids, the lipid moiety of iturin.
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Affiliation(s)
- C Feignier
- Laboratoire de Biochimie Microbienne, Université Claude Bernard, Lyon I, Villeurbanne, France
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289
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Abstract
Magainin peptides, isolated from Xenopus skin, kill bacteria by permeabilizing their cell membranes whereas they do not lyse erythrocytes. To elucidate the rationale for this membrane selectivity, we compared the effects of the membrane lipid composition and the transmembrane potential on the membrane-lytic power of magainin 2 with that of hemolytic melittin. The activity of magainin to zwitterionic phospholipids constituting the erythrocyte surface was extremely weak compared with that of melittin, and acidic phospholipids are necessary for effective action. The presence of sterols reduced the susceptibility of the membrane to magainin. The generation of an inside-negative transmembrane potential enhanced magainin-induced hemolysis. We can conclude that the absence of any acidic phospholipids on the outer monolayer and the abundant presence of cholesterol, combined with the lack of the transmembrane potential, contribute to the protection of erythrocytes from magainin's attack.
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Affiliation(s)
- K Matsuzaki
- Faculty of Pharmaceutical Sciences, Kyoto University, Japan
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290
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Abstract
In a previous study (J. O'Rear, L. Alberti, and R. M. Harshey, J. Bacteriol. 174:6125-6137, 1992) we reported the isolation of several transposon mutants of Serratia marcescens 274 that were defective either in swarming alone or in both swimming and swarming motility. All the nonflagellate (Fla-) mutants, while defective in both types of motility, were able to spread rapidly on the surface of low-agar (0.35%) media. We show here that some of the swarming-defective mutants are defective in the production of serrawettin W1, an extracellular cyclic lipopeptide produced by S. marcescens 274. When combined with a Fla defect, the serrawettin (Swt) mutants are deficient in spreading on low-agar media. The spreading deficiency can be overcome by serrawettin supplied extracellularly. Introduction of Fla defects into chemotaxis mutants does not affect this mode of surface translocation. These results suggest that spreading may be a passive form of translocation. We also report that swarming defects in all mutants showing a Dps phenotype (able to swarm within the inoculated area but unable to move outward) in the earlier study can be overcome by changing the commercial source of agar.
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Affiliation(s)
- T Matsuyama
- Department of Bacteriology, Niigata University School of Medicine, Japan
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291
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Fiss EH, Yu S, Jacobs WR. Identification of genes involved in the sequestration of iron in mycobacteria: the ferric exochelin biosynthetic and uptake pathways. Mol Microbiol 1994; 14:557-69. [PMID: 7885234 DOI: 10.1111/j.1365-2958.1994.tb02189.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Mycobacteria produce two siderophores, mycobactin and exochelin. Mycobacterium smegmatis mutants defective in the production of exochelin were isolated using agar medium containing chrome azural S for the sensitive detection of siderophores. Cosmids of genomic libraries from M. smegmatis and Mycobacterium bovis BCG were screened for complementation of the mutation. Subcloning of the complementing M. smegmatis cosmid identified a 4.3 kb fragment required for restoring exochelin biosynthesis. Sequencing of the DNA revealed four open reading frames whose genes were named fxuA, fxuB, fxuC, and fxbA. FxuA, FxuB, and FxuC share amino acid sequence homology with the iron permeases FepG, FepC, and FepD from Escherichia coli, respectively. Deletion analysis identified fxbA as the gene required to restore exochelin biosynthesis in our mutant. Although fxbA does not share amino acid sequence homology with any of the published sequences for siderophore biosynthetic genes, it does show limited homology with the phosphoribosylglycineamide formyltransferases (GAR enzymes) and methionyl-tRNA formyltransferase over a limited region of the sequence, suggesting that fxbA may code for an enzyme which adds a formyl group in the synthesis of exochelin. A fusion of fxbA with the E. coli lacZ gene demonstrated regulation of gene expression by iron. The ability of M. smegmatis mutants to produce mycobactin in the absence of exochelin supports the hypothesis that exochelin is not a precursor of mycobactin and suggests that the siderophores have independent biosynthetic pathways. In addition, complementation of the M. smegmatis mutant with the BCG cosmid restored the synthesis of the M. smegmatis exochelin, demonstrating the use of M. smegmatis as a surrogate host for analysis of exochelins from slow-growing mycobacteria.
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Affiliation(s)
- E H Fiss
- Department of Microbiology and Immunology, Howard Hughes Medical Institute, Albert Einstein College of Medicine, Bronx, New York 10461
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292
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Morikawa M, Daido H, Pongpobpibool S, Imanaka T. Construction of a new host-vector system in Arthrobacter sp. and cloning of the lipase gene. Appl Microbiol Biotechnol 1994; 42:300-3. [PMID: 7765770 DOI: 10.1007/bf00902732] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Arthrobacter sp. strain MIS38 was transformed with a shuttle vector containing the kanamycin resistant gene kan (derived from Tn5) by an electroporation method. This shuttle vector is from Brevibacterium lactofermentum and Escherichia coli, pULRS8. The following optimal condition of electroporation was determined. A square wave pulse of 1 kV/cm electric field strength for 0.5 ms duration yielded 3 x 10(5) transformants/micrograms plasmid DNA. The number of transformants increased with the amount of DNA over the range 0.01-5 micrograms. This host-vector system was then used successfully to clone and express a lipase gene from Arthrobacter sp. strain MIS38 into both Arthrobacter sp. MIS38 and E. coli JM109.
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Affiliation(s)
- M Morikawa
- Department of Biotechnology, Faculty of Engineering, Osaka University, Japan
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293
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Martínez-Bueno M, Maqueda M, Gálvez A, Samyn B, Van Beeumen J, Coyette J, Valdivia E. Determination of the gene sequence and the molecular structure of the enterococcal peptide antibiotic AS-48. J Bacteriol 1994; 176:6334-9. [PMID: 7929005 PMCID: PMC196975 DOI: 10.1128/jb.176.20.6334-6339.1994] [Citation(s) in RCA: 105] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The structural gene of the enterococcal peptide antibiotic AS-48 (as-48) has been identified and cloned by using two degenerate 17-mer DNA oligonucleotides on the basis of the amino acid sequences of two peptides obtained by digestion of the antibiotic with Glu-C endoproteinase. That as-48 gene codes for a 105-amino-acid prepeptide, giving rise to a 70-amino-acid mature protein. Comparative analysis demonstrated that the 16-amino-acid sequence of one of the AS-48 Glu-C peptides, designated V8-5, was composed of a 12-amino-acid sequence corresponding to the C-terminal end sequence (from isoleucine +59 to tryptophan +70 [I+59 to W+70]) of the prepeptide and terminated in four residues forming the N terminus (M+1 to E+4) of a putative AS-48 propeptide. These data, combined with the characteristics of the gene sequence, strongly suggested that the antibiotic peptide was a 70-residue cyclic molecule. We propose that the AS-48 translated primary product is very likely submitted to a posttranslational modification during secretion (i) by an atypical or a typical signal peptidase that cleaves off a 35-residue or shorter signal peptide, respectively, from the prepeptide molecule and (ii) by the linkage of the methionine residue (M+1) to the C-terminal tryptophan residue (W+70) to obtain the cyclic peptide (a tail-head linkage).
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Affiliation(s)
- M Martínez-Bueno
- Centre d'Ingénierie des Protéines, Institut de Chimie B6, Université de Liège, Sart Tilman, Belgium
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294
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Abstract
Bac7 is a 7 kDa proline- and arginine-rich antimicrobial peptide which was purified from bovine neutrophils. We have used PCR to clone the cDNA of Bac7 precursor, a polypeptide of 21,569 Da. This cDNA is highly conserved in the 5' region, with respect to the corresponding region in the precursors of several other structurally unrelated myeloid antimicrobial peptides. Furthermore, a 148 nt non-coding region at the 3' end is 75% homologous to a corresponding region of the cDNA of the precursor of PR-39, a porcine antibacterial peptide which is also proline- and arginine-rich.
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Affiliation(s)
- M Scocchi
- Laboratorio Nazionale Consorzio Interuniversitario Biotecnologie, AREA Science Park, Trieste, Italy
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295
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Samyn B, Martinez-Bueno M, Devreese B, Maqueda M, Gálvez A, Valdivia E, Coyette J, Van Beeumen J. The cyclic structure of the enterococcal peptide antibiotic AS-48. FEBS Lett 1994; 352:87-90. [PMID: 7925951 DOI: 10.1016/0014-5793(94)00925-2] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The complete primary structure of the peptide antibiotic AS-48 produced by Enterococcus faecalis has been determined by chemical degradation analysis. The cyclic nature of this 70 residues containing peptide was demonstrated by plasma desorption mass analysis of the generated peptides and electrospray ionisation mass analysis of the native polypeptide. As far as we know, this is the first example of an antibiotic protein cyclised by a tail-head peptide bond formation and not by branching of the polypeptide side chains.
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Affiliation(s)
- B Samyn
- Department of Biochemistry, Physiology and Microbiology, University Gent, Belgium
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296
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Abstract
Figure 2 illustrates an outline of the cellular and humoral defense systems in limulus. On the basis of the knowledge described above, it is suggested that granular components present in L and S granules in the hemocytes play a decisive role in the biological defense for this animal. The isolated L granules contain at least three clotting factors plus coagulogen as the major component. The known anti-LPS factor and a number of additional unknown protein components are also present in the L granules. On the other hand, the isolated S granules contain antimicrobial tachyplesins as the major component, in addition to six unidentified proteins. We speculate that the L-granule-derived protein components, which probably contain all the factors essential for the Limulus clotting system participate, in immobilizing invading microbes, and that the S-granule-derived tachyplesins contribute to a self-defense system against invaders. Although we have not mentioned hemolymph plasma components, there are many humoral factors, such as proteinase inhibitors, alpha 2-macroglobulin, various lectins, C-reactive protein, and polyphemin, all of which are important for antimicrobial defense. Furthermore, Liu and colleagues have reported several endotoxin-binding proteins and a cell-adhesion protein found in the Limulus hemocytes. Although the exact functions of these substances are unknown, they may act in concert with other components to provide biological defense for the animal. Nevertheless, compared to our knowledge of mammalian blood cells, much less remains to be learned of biological/physiological events in horseshoe crab hemocytes.
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Affiliation(s)
- S Iwanaga
- Department of Biology, Faculty of Science, Kyushu University, Fukuoka, Japan
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297
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Lagerkvist A, Stewart J, Lagerström-Fermér M, Landegren U. Manifold sequencing: efficient processing of large sets of sequencing reactions. Proc Natl Acad Sci U S A 1994; 91:2245-9. [PMID: 8134382 PMCID: PMC43347 DOI: 10.1073/pnas.91.6.2245] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Automated instruments for DNA sequencing greatly simplify data collection in the Sanger sequencing procedure. By contrast, the so-called front-end problems of preparing sequencing templates, performing sequencing reactions, and loading these on the instruments remain major obstacles to extensive sequencing projects. We describe here the use of a manifold support to prepare and perform sequencing reactions on large sets of templates in parallel, as well as to load the reaction products on a sequencing instrument. In this manner, all reaction steps are performed without pipetting the samples. The strategy is applied to sequencing PCR-amplified clones of the human mitochondrial D-loop and for detection of heterozygous positions in the human major histocompatibility complex class II gene HLA-DQB, amplified from genomic DNA samples. This technique will promote sequencing in a clinical context and could form the basis of more efficient genomic sequencing strategies.
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Affiliation(s)
- A Lagerkvist
- Beijer Laboratory, Department of Medical Genetics, Uppsala Biomedical Center, Sweden
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298
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Kupke T, Kempter C, Gnau V, Jung G, Götz F. Mass spectroscopic analysis of a novel enzymatic reaction. Oxidative decarboxylation of the lantibiotic precursor peptide EpiA catalyzed by the flavoprotein EpiD. J Biol Chem 1994; 269:5653-9. [PMID: 8119901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The epidermin biosynthetic reaction between the flavoprotein EpiD and the precursor peptide EpiA was investigated by reversed-phase chromatography and ion spray mass spectrometry. Several products with molecular masses 46 and 104 Da less than that of EpiA were observed; these results were confirmed by using an MBP-EpiD fusion protein as enzyme and the mutant peptides EpiAR-1Q and K-EpiA as substrates. The reaction was inhibited by Zn2+ ions. Modifications were localized in the C-terminal fragment of EpiA as shown by factor Xa cleavage of the products followed by mass spectrometry analysis. In addition, EpiD reacted with the precursor peptides and with proepidermin, indicating that the leader peptide is not necessary for the recognition of EpiA by EpiD. Sequence analysis of modified proepidermin revealed that at least the amino acids Ile(+1)-Tyr+20 are unmodified. The observed decrease in mass of 46 Da and the modification at the C terminus of EpiA is in agreement with the proposed enzymatic function of EpiD, the oxidative decarboxylation of the precursor peptide. In addition, the increased absorbance at 260 nm of the modified peptides indicates the presence of a thioenol group in the C-terminal proepidermin.
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Affiliation(s)
- T Kupke
- Mikrobielle Genetik, Universität Tübingen, Federal Republic of Germany
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299
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Abstract
A study of polymorphisms of mitochondrial DNA (mtDNA) of West African N'Dama (Bos taurus) and East African Zebu (B. indicus) cattle was carried out to obtain information on maternal phylogenetic relationships between these breeds. A relatively large sample size was made possible by using polymerase chain reaction (PCR) amplification of DNA prepared from small blood samples to generate fragments of two known polymorphic mtDNA regions, one within the gene encoding subunit 5 of NADH dehydrogenase and one encompassing the entire D-loop. This approach allowed us to achieve a higher resolution restriction analysis on mtDNA from more animals than would have been possible by conventional methods. PCR-amplified mtDNA of 58 animals from five populations was examined at 26 restriction sites by 16 enzymes. In this way 154 nucleotides of mtDNA were scanned for polymorphism. Six polymorphic sites were located by this means, five of which were within the D-loop and one of which was within the NADH dehydrogenase 5 gene. None of the polymorphisms observed could be considered typical of breed or type.
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300
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Sanchez J, Solorzano RM, Holmgren J. Extracellular secretion of STa heat-stable enterotoxin by Escherichia coli after fusion to a heterologous leader peptide. FEBS Lett 1993; 330:265-9. [PMID: 8375497 DOI: 10.1016/0014-5793(93)80885-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The mature 19-amino acid STa heat-stable enterotoxin of E. coli has a preceding peptide of 53 amino acids which contains two domains called Pre (aa 1-19) and Pro (aa 20-53) sequences, proposed to be essential for extracellular toxin release by this host. The Pro sequence, however, has been proven not be indispensable for this process since Pro deletion mutants secrete STa. To find out if Pre and/or other unremoved natural STa flanking sequences are responsible for toxin secretion in those mutants we genetically fused mature STa directly to the leader peptide of the periplasmic E. coli heat-labile enterotoxin B-subunit (LTB). Expression of this gene fusion resulted in extracellular secretion of biologically active STa by E. coli independently of natural STa neighboring genetic sequences. Moreover, these results suggest that STa might be able to gain access to the extracellular milieu simply upon its entry into the E. coli periplasm once guided into this compartment by the LTB leader peptide. To test if extracellular secretion in this fashion might be extended to other disulfide bond-rich small peptides, the 13 amino acid conotoxin GI and a non-enterotoxic STa-related decapeptide were cloned. None of the two peptides was found in culture supernatants, in spite of high structural homology to the toxin. Failure to be secreted most likely leads to degradation as peptides were also not detected in bacterial sonicates. We hypothesize that cysteine-rich peptides must have an amino acid length and/or number of disulfide bridges closer to those in STa for them to follow this toxin secretory pathway in E. coli.
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Affiliation(s)
- J Sanchez
- Centro de Investigación sobre Enfermedades Infecciosas, Instituto Nacional de Salud Pública, Cuernavaca, Morelos, Mexico
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