Subunit positioning and transmembrane helix organisation in the core dimer of photosystem II

Recently 3D structural models of the photosystem II (PSII) core dimer complexes of higher plants (spinach) and cyanobacteria (Synechococcus elongatus) have been derived by electron [Rhee et al. (1998) Nature 396, 283-286; Hankamer et al. (2001) J. Struct. Biol., in press] and X-ray [Zouni et al. (2001) Nature 409, 739-743] crystallography respectively. The intermediate resolutions of these structures do not allow direct identification of side chains and therefore many of the individual subunits within the structure are unassigned. Here we review the structure of the higher plant PSII core dimer and provide evidence for the tentative assignment of the low molecular weight subunits. In so doing we highlight the similarities and differences between the higher plant and cyanobacterial structures.

Streptococcus mutans strain N produces a novel low molecular mass non-lantibiotic bacteriocin

Streptococcus mutans strain N was shown to have bacteriocin production and immunity characteristics consistent with those of Group I mutacin-producing strains of S. mutans. The bacteriocin mutacin N was purified from agar cultures of S. mutans strain N using XAD andp6 reversed phase chromatography. The molecular mass of mutacin N was 4806 Da and the entire 49 amino acid sequence was determined by N-terminal sequencing. Database searches indicate that mutacin N is a novel bacteriocin, but with some homology to the protein IIC domain of a hypothetical sugar-phosphotransferase enzyme from Acholeplasma florum.

The ordered visual transduction complex of the squid photoreceptor membrane

The study of visual transduction has given invaluable insight into the mechanisms of signal transduction by heptahelical receptors that act via guanine nucleotide binding proteins (G-proteins). However, the cyclic-GMP second messenger system seen in vertebrate photoreceptor cells is not widely used in other cell types. In contrast, the retina of higher invertebrates, such as squid, offers an equally accessible transduction system, which uses the widespread second messenger chemistry of an increase in cytosolic calcium caused by the production of inositol-(1,4,5)-trisphosphate (InsP3) by the enzyme phospholipase C, and which may be a model for store-operated calcium influx. In this article, we highlight some key aspects of invertebrate visual transduction as elucidated from the combination of biochemical techniques applied to cephalopods, genetic techniques applied to flies, and electrophysiology applied to the horseshoe crab. We discuss the importance and applicability of ideas drawn from these model systems to the understanding of some general processes in signal transduction, such as the integration of the cytoskeleton into the signal transduction process and the possible modes of regulation of store-operated calcium influx.

Purification, partial characterization and peptide sequences of vitellogenin from a reptile, the tuatara (Sphenodon punctatus)

Vitellogenin (Vg), a major precursor to egg yolk proteins, was purified from plasma of an estradiol-treated female tuatara (Sphenodon punctatus) by MgCl2-EDTA precipitation and DEAE-cellulose chromatography. The amino acid composition of tuatara Vg is similar to that of other vertebtate Vgs and contains a large proportion of serine (13.7 mol/100 mol of total amino acid). The amino acid sequences of the N-terminus of mature Vg (33 residues) and of several trypsin- and CNBr-generated peptides were determined. Six peptide sequences obtained from tuatara Vg could be aligned with Vg sequences from other vertebrates. Reduced and non-reduced forms of tuatara Vg have the same apparent molecular mass (approximately 218 kDa) when resolved by SDS-PAGE, indicating that inter-chain disulfide bonds are not a feature of the molecule in this species. Western blot analysis with anti-tuatara Vg antiserum indicated that at least some epitopes are shared among Vgs of turtle, alligator and tuatara.

Isolation, cloning, and characterisation of a trp homologue from squid (Loligo forbesi) photoreceptor membranes

The invertebrate phototransduction system is a valuable model of the ubiquitous inositol lipid signalling system. Taking advantage of the ability to obtain relatively large amounts of retinal material from the cephalopod eye, partial protein sequence data were obtained for a 92-kDa component isolated from a detergent-insensitive cytoskeletal fraction of a squid retinal microvillar membrane preparation. Degenerate oligonucleotides, designed on the basis of these sequence data, were used to isolate a full-length cDNA, encoding the 92-kDa component, using both cDNA library screening and 5'-rapid amplification of cDNA ends (5'-RACE) techniques. Comparison of the amino acid sequence encoded by this cDNA with entries in the OWL composite protein sequence database reveals greatest sequence similarity with the products of the Drosophila trp and trpl genes. Greatest variation from the Drosophila Trp protein is seen in the carboxyl-terminal region, which is considerably truncated in the squid protein and which accounts for most of the substantial difference in molecular weight seen between these proteins. This variation may be significant as the carboxyl-terminal domain has been shown to be in the regulation of several ligand-gated channels. The carboxyl-terminal domain has been expressed and shown to interact with calmodulin in a calcium-dependent fashion, thereby supporting this hypothesis. The likely occurrence of other homologues in a variety of systems suggests that this is a novel and important family of regulated ion channels involved in calcium signalling.

Analysis of chaperonin-containing TCP-1 subunits in the human keratinocyte two-dimensional protein database: further characterisation of antibodies to individual subunits

The chaperonin-containing TCP-1 (CCT), found in the eukaryotic cytosol, is currently the focus of extensive research. CCT consists of at least eight different subunit types encoded by independent but related genes, and a set of antibodies that recognise individual subunits has proved useful in the characterisation and functional analysis of CCT. These antibodies were used to identify subunits of CCT in the human keratinocyte two-dimensional protein database. Accurate values for the pI and molecular mass of human CCT subunits were determined from the database, and biological data was obtained regarding changes in subunit levels in response to extracellular agents and growth conditions. The second part of the study describes the characterisation of seven monoclonal antibodies raised against mouse TCP-1, also known as CCT alpha, using a combination of epitope mapping and immunoblot analysis of protein extracts from different species and tissue types. Some antibodies were not monospecific for TCP-1, and a number of epitope-related proteins were identified.

Identification and partial characterization of alpha 2-macroglobulin from the tuatara (Sphenodon punctatus)

alpha 2-Macroglobulin (alpha 2-M), a large molecular mass proteinase-binding protein, was identified in plasma from tuatara (Sphenodon), a rare reptile endemic to New Zealand. In this genus, alpha 2-M constitutes 11-13% of total plasma protein (approximately 2.2-3.9 mg/mL). Analysis of blood samples collected at approximately monthly intervals from individual tuatara indicated that the plasma level of alpha 2-M remains fairly constant. The subunits of tuatara alpha 2-M have an apparent molecular mass of approximately 160 kDa as determined by SDS-polyacrylamide gel electrophoresis and the intact protein is an oligomer that contains inter-chain disulfide bonds. N-terminal sequence analyses of tuatara alpha 2-M revealed a distinct similarity to alpha-macroglobulins of other vertebrates and that at least two types of alpha 2-M subunits are present in plasma of tuatara.

A beta-subclass phosphatidylinositol-specific phospholipase C from squid (Loligo forbesi) photoreceptors exhibiting a truncated C-terminus

A PCR-based strategy has been used to isolate a full length cDNA encoding a phosphatidylinositol-specific phospholipase C from a sized cDNA squid (Loligo forbesi) retinal library. The predicted protein sequence contains 875 amino acids, with calculated M(r) 98,181, and has marked similarity with PLC beta-isoforms, including conservation of the 'X' and 'Y' regions. It is unique in having a major C-terminal truncation. A major protein of apparent M(r) 120,000 estimated by SDS-PAGE has been isolated from squid photoreceptors and identified by partial protein sequence analysis to correspond to the protein sequence predicted from the cDNA clone. This protein has been shown to hydrolyse phosphatidylinositol 4,5-bisphosphate. It is not yet clear whether this represents the major light-activated PLC in squid vision.

Identification of a 130-kDa albumin in tuatara (Sphenodon) and detection of a novel albumin polymorphism

Electrophoretic, immunochemical, and protein sequence analyses were performed on plasma albumin of the tuatara (Sphenodon), a rare reptile endemic to New Zealand. The analyses revealed that, unlike other terrestrial vertebrates, tuatara do not seem to possess a 60- to 75-kDa plasma albumin. The common form of plasma albumin in this genus has an apparent molecular mass of 130 kDa, making it by far the largest albumin reported for any terrestrial vertebrate. Starch gel electrophoresis of samples from tuatara on 24 of the 30 islands inhabited by this genus resolved two forms of the 130-kDa albumin (albumins A and C). A third albumin of approximately 170 kDa (albumin B), reflecting a novel alloalbuminemia, was found in tuatara in three geographically isolated populations. Albumin A appears to be restricted to populations at the southern extremity of the tuatara's distribution, while albumin C was found in all but four (southern) populations. Possible explanations for the origin and distribution of these albumins are discussed.

Purification and properties of zinc-metallophospholipase C from Pseudomonas fluorescens

Phospholipase C produced by Pseudomonas fluorescens, isolated as a laboratory contaminant, has been purified to apparent homogeneity by ammonium sulphate fractionation, anion-exchange and size-exclusion chromatographies. The apparent molecular mass of the purified polypeptide was 39.5 kDa. Purified preparations of phospholipase C were used to characterize its enzymic properties and to obtain amino acid sequence of the N-terminus of the molecule. The P. fluorescens phospholipase C hydrolysed PtdEtn, PtdCho and PtdSer (PtdEtn > PtdCho >> PtdSer) and was relatively thermostable. The enzyme was inactivated in the presence of chelating agent o-phenanthroline and the activity restored after addition of zinc. Properties of this enzyme and in particular the requirement for zinc ions for the activity, revealed similarity with the well characterised Bacillus cereus phospholipase C. Similarities with other bacterial and mammalian enzymes reported to be related to the B. cereus type are discussed.

Differential feeding-related regulation of ubiquitin and calbindin9kDa in rat duodenum

Analyses of the calcium-binding protein, calbindin9kDa, purified to apparent homogeneity (SDS-PAGE) from rat duodenum, revealed variable contamination by two other 9 kDa proteins (up to 0.2 mol equivalent each) which were identified as ubiquitin and its C-terminal variant, des-Gly-Gly-ubiquitin. We found that the co-purification of these proteins did not reflect a tight molecular interaction but instead their unexpectedly similar physical characteristics in nondenaturing conditions. Like calbindin9kDa, free ubiquitin was abundant (1% and 0.4% of soluble protein, respectively) in duodenum mucosa of 7-8-week-old rats and its concentration varied daily and with feeding status. In rats fed from midnight to 8.30 a.m., the ubiquitin concentration was specifically higher at 10 pm than at 10 a.m. (11.2 +/- 0.7 and 7.7 +/- 0.8 nmol per g wet weight, respectively, P < 0.02), whereas calbindin9kDa tended towards an opposite variation (18.0 +/- 1.9 and 21.8 +/- 1.7 nmol per g, respectively). Based on its unusually high abundance and novel feeding-related variations, ubiquitin must have an important functional role in the rat duodenum which is distinctly regulated from the calcium transport-associated role of calbindin9kDa.

Elucidation of the structure of SA-FF22, a lanthionine-containing antibacterial peptide produced by Streptococcus pyogenes strain FF22

The antibacterial peptide SA-FF22, produced by the pathogen Streptococcus pyogenes strain FF22 was purified and features of its primary and secondary structure were characterised. Mass spectrometry demonstrated the pure peptide had a mass of 2794Da while, amino acid analysis revealed the presence of the unusual, thioether amino acids lanthionine and 3-methyllanthionine; thus SA-FF22 is a member of the group of antibacterial polypeptides termed lantibiotics. Furthermore, amino acid sequencing showed a unique sequence which was blocked at position 23 by a residue of the unsaturated amino acid 2,3-didehydrobutyrine. Carboxypeptidase-Y digestion could be used to demonstrate that serine occupies the C-terminal position only after complete oxidation of the thioether amino acid bridges, suggesting that the three-dimensional structure of the native peptide may prevent access of the enzyme to the C-terminus. Fragmentation of the native peptide with a variety of proteolytic enzymes failed to yield a peptide containing less than all three of the cross-linked lanthionine and methyllanthionine residues and demonstrated that all three thioether bridges overlapped. Analysis of the circular dichroism of SA-FF22 in various concentrations of 2,2,2-trifluoroethanol in water, SDS micelles and in the presence of artificial phospholipid vesicles suggested that there is significant change in its secondary structure from aqueous to lipophilic environments.

Identification of six Tcp-1-related genes encoding divergent subunits of the TCP-1-containing chaperonin

BACKGROUND

TCP-1 is a 60 kD subunit of a cytosolic hetero-oligomeric chaperone that is known to be involved in the folding of actin and tubulin. This protein is a member of the chaperonin family, which includes Escherichia coli GroEL, the mitochondrial heat-shock protein Hsp60, the plastid Rubisco-subunit-binding protein and the archaebacterial protein TF55. These chaperonins assist the folding of proteins upon ATP hydrolysis.

RESULTS

Using two-dimensional gel analysis, we have identified nine different subunits of TCP-1-containing chaperonin complexes from mammalian testis and seven different subunits of such complexes from mouse F9 cells. We have isolated full-length mouse cDNAs encoding six novel TCP-1-related polypeptides and show that these cDNAs encode subunits of the TCP-1-containing cytosolic chaperonin. These subunits are between 531 and 545 residues in length. Their sequences are 25-36% identical to one another, 27-35% identical to that of TCP-1 and 32-39% identical to that of the archaebacterial chaperonin, TF55. We have named these genes, Cctb, Cctg, Cctd, Ccte, Cctz and Ccth, which encode the CCT beta, CCT gamma, CCT delta, CCT epsilon, CCT zeta and CCT eta subunits, respectively, of the 'Chaperonin Containing TCP-1' (CCT). All the CCT subunits contain motifs that are also shared by all other known chaperonins of prokaryotes and eukaryotic organelles, and that probably relate to their common ATPase function.

CONCLUSION

It is likely that each CCT subunit has a specific, independent function, as they are highly diverged from each other but conserved from mammals to yeast. We suggest that the expansion in the number of types of CCT subunit, compared with other chaperonins, has allowed CCT to carry out the more complex functions that are required for the folding and assembly of highly evolved eukaryotic proteins.

Isolation and sequencing of deer and sheep insulin-like growth factors-I and -II

We have developed a simple method for the isolation of highly purified cervine (c) and ovine (o) insulin-like growth factors-I (IGF-I) and -II. The IGFs were isolated from acidified serum by cation exchange chromatography and then purified by gel filtration, chromatofocusing, and reverse-phase chromatography. The IGF preparations are > 95% pure. The cIGF-I preparation contains < 0.056% cIGF-II and the oIGF-I preparation contains < 0.01% oIGF-II. Both the IGF-II preparations contain < 0.01% IGF-I. The amino acid sequence of cIGF-I has two differences when compared with human (h) IGF-I. The cIGF-II sequence, which is identical to bovine IGF-II, has three differences when compared with hIGF-II.

Structural requirements of phosphatidylinositol-specific phospholipase C delta 1 for enzyme activity

Phosphatidylinositol-specific phospholipase C delta 1 isozyme of phosphoinositol-specific phospholipase C has been used for studies of structural requirements for the catalytic function. The enzyme was expressed in a bacterial system and purified to homogeneity. Using a combination of deletion mutant analysis and limited proteolysis, it was found that the large proportion of the molecule participated in formation of a catalytic domain (residues 139-756); it included regions of high and low conservation with other phospholipase-C molecules. These studies also showed that the residues spanning regions of conservation, designated as X and Y, were exposed and highly susceptible to proteolysis by trypsin. Two of the fragments resulting from the cleavage (30 kDa and 40 kDa) interacted and, under non-denaturing conditions, formed a protein of 70 kDa.

An exo-beta-(1,3)-glucanase of Candida albicans: purification of the enzyme and molecular cloning of the gene

A nucleotide sequence encoding an exo-beta-(1,3)-glucanase was cloned from a library of genomic DNA of Candida albicans ATCC 10261. The sequenced gene encodes a protein of 438 amino acid residues. The amino terminal and an internal peptide sequence of the enzyme matched with deduced sequences within the cloned gene. Analysis of the sequence indicated that the nascent protein is processed during secretion by the signal peptidase and a Kex2-like proteinase, yielding a predicted mature enzyme of 400 residues. There is 58% identity and 85% similarity between the amino acid sequences of this exoglucanase and the homologous enzyme of Saccharomyces cerevisiae. An antiserum to the purified exoglucanase cross-reacted with the S. cerevisiae exoglucanase and a similar protein secreted by other C. albicans strains and Candida species. There are no sites for N-linked glycosylation in the sequence and this is consistent with the carbohydrate content of the secreted enzyme. Putative upstream promoter elements are associated with the gene. Southern analysis of the gene indicated that it was present at one copy per genome and that the diploid genome of C. albicans ATCC 10261 is heterozygous at this locus for a BglII RFLP. A 2.5 kb mRNA transcript was detected by Northern analysis and gene expression, as monitored by Northern and Western blots, reflected the growth rates of the cultures.

A second gene for a secreted aspartate proteinase in Candida albicans

The gene (PRA11) encoding a secreted aspartate proteinase of Candida albicans has been cloned and sequenced. The nucleotide and deduced amino acid sequences of PRA11 are 77 and 73% identical, respectively, with the reported sequences of PRA10 also cloned from C. albicans. Southern analyses indicated that the genome of each strain examined (ATCC 10231 and ATCC 10261) contains PRA10 and PRA11. Northern (RNA) analyses showed that PRA11 was expressed at a much higher level than was PRA10 when secretion of the proteinase by strain ATCC 10261 was induced with albumin.

The gamma-subunit of the principal G-protein from squid (Loligo forbesi) photoreceptors contains a novel N-terminal sequence

The squid (Loligo forbesi) visual system presents as accessible a system for study of G-protein mediated signal transduction as the vertebrate rod outer segment with the added advantage that the major G-protein is a member of the Gq-class. Here the cDNA clone encoding the gamma-subunit of this G-protein is reported, thereby completing the molecular cloning of the heterotrimeric G-protein. The deduced protein structure of G-gamma has relatively little sequence identity with known mammalian counterparts particularly in comparison with the relatively high degree found for both the alpha- and beta-subunits of this protein. In particular, the N-terminus of the squid visual G-gamma contains a repetitive, highly charged region, rich in lysine and glutamate, that has no parallel in other G-proteins. The amino acid sequence of a number of peptides derived by chemical cleavage of G-gamma accounted for much of the protein sequence predicted from the cDNA, including the unusual N-terminal region.

Lantibiotic-mediated anti-lactobacillus activity of a vaginal Staphylococcus aureus isolate

Staphylococcus aureus strain 26 inhibited the growth of 23 of 26 lactobacilli of endocervical origin, but only two of 17 staphylococci, in deferred antagonism tests. The inhibitory agent, a bacteriocin-like inhibitory substance (BLIS) named staphylococcin Au-26, was obtained from vigorously shaken liquid cultures containing a 0.1% (v/v) supplement of Tween 80 and was purified by chromatographic fractionation on XAD-2, carboxymethyl Sephadex and reversed phase HPLC. The molecular mass of staphylococcin Au-26 was estimated by SDS-PAGE to be approx. 2700. The detection of lanthionine residues in the molecule, the high stability to heating at acidic but not alkaline pH values and inactivation by proteinases indicate that staphylococcin Au-26 is a member of the lantibiotic class of peptide antibiotics--the first reported to be produced by a S. aureus strain. Primary sequence analysis showed that the N-terminus of the molecule is isoleucine, a characteristic also displayed by the lantibiotics nisin, epidermin and gallidermin.

L-asparaginase from developing seeds of Lupinus arboreus

Asparaginase (EC 3.5.1.1) activity reached a maximum 40 days post anthesis in developing seeds of Lupinus arboreus and this correlated with the appearance of other ammonia assimilatory enzymes. Asparaginase, purified from these developing seeds, was resolved into three isoforms, designated asparaginases A, B and C. A major protein species in asparaginase A preparations co-focussed with enzyme activity on an isoelectric focussing gel. When analysed by SDS-PAGE, asparaginase isoforms A and B each yielded several polypeptides with M(r)s in the 14,000 to 19,000 ranged. These peptides are fragmentation products of an M(r) 36,000 asparaginase subunit. Polyclonal antibodies raised against asparaginase isoforms A and B precipitated asparaginase activity from a partially purified L. arboreus seed extract. Immunoaffinity chromatography recovered polypeptides with M(r)s between 14,000 and 19,000. Partial protein sequences were obtained for these asparaginase polypeptides.

A comparison of the structural polypeptides of three iridescent viruses (types 6, 9, and 16) and the mapping of the DNA region coding for their major capsid polypeptides

The iridoviruses from Wiseana cervinata (WIV, type 9), Costelytra zealandica (CzIV, type 16) and Chilo suppressalis (CIV, type 6) were compared by SDS-PAGE and Western protein blotting for antigenic determinants. The major capsid proteins were isolated and oligonucleotide probes were synthesized from the partial amino acid sequences. The DNA regions coding for the major capsid proteins of WIV (VP52), CzIV (VP53) and CIV (VP50) were located by hybridization of the oligonucleotide probes to blots of the viral DNA. The major capsid protein was used as the zero point for the proposed linearized maps of these viruses. Using antibody and 125I-labelling, several proteins were identified as being on the surface of the virion. It was also shown that CIV was not as antigenically distinct from these two viruses as previously reported.

The purification of ovine pancreatic lipase that is free of colipase using an improved delipidation method

A modified procedure for the purification of ovine pancreatic lipase (triacylglycerol acyl-hydrolase, EC3.1.1.3) is described. The method is more rapid and more reproducible than that reported previously and results in a pure lipase preparation, that gives a better yield at the same specific activity, free of colipase and uncontaminated by lipid. The procedure involves the preparation of a lipid-free acetone powder from fresh pancreas without the use of chloroform or butanol as was used in the procedure described earlier. The aqueous purification of the lipase from the delipidated powder is similar to that described earlier, but includes the use of beta-mercaptoethanol and uses salt gradient elution from CM-Sepharose. An assay procedure for lipase is reported involving the extraction of released free fatty acids with chloroform/methanol before titrating with sodium hydroxide. A modification of this assay is used for the determination of colipase. The above assay procedure is compared to the potentiometric method reported previously. Polyacrylamide gel, amino acid composition analysis and N-terminal sequence data for the purified ovine lipase are presented.

Structure of equine corticotropin releasing factor

A 41 amino acid peptide, probably identical in structure to human corticotropin releasing factor, was isolated from 70 equine hypothalami by methanol extraction, immunoaffinity chromatography and single step of reverse phase HPLC. The amino acid sequence was determined by gas phase sequence analysis. Probable carboxyl terminal amidation was demonstrated by similar retention times for equine and human corticotropin releasing factor on reverse phase HPLC at pH 8. The likely structure of equine corticotropin releasing factor is: Ser-Glu-Glu-Pro-Pro- Ile-Ser-Leu-Asp-Leu-Thr-Phe-His-Leu-Leu-Arg-Glu-Val-Leu-Glu-Met-Ala-Arg- Ala-Glu - Gln-Leu-Ala-Gln-Gln-Ala-His-Ser-Asn-Arg-Lys-Leu-Met-Glu-Ile-Ile-NH2. The purified peptide is equipotent with human corticotropin releasing factor in an in vitro bioassay and in a human plasma binding protein assay.

The putative single-stranded DNA-binding protein of the filamentous bacteriophage, Ifl. Amino acid sequence of the protein and structure of the gene

The protein product corresponding to the gene located in the region of the coliphage Ifl genome shown to contain the code for the single-stranded DNA (ssDNA)-binding proteins of all filamentous phages so far studied has been isolated from infected bacterial cells and its amino acid sequence determined. The mature protein contains 95 amino acids (calculated molecular mass 10553 Da). Its sequence corresponds to that predicted from the DNA sequence but lacks the initiating methionine residue. Although there is little direct sequence homology between the phage Ifl protein and the ssDNA-binding proteins of the other filamentous phages that have been studied, computer-based comparisons of various physical and structural parameters showed that the phage Ifl protein contains a domain that is closely related to domains in the coliphage T4 gene 32 protein and the Pseudomonas phage Pfl ssDNA-binding protein and suggest that the Ifl protein does have a ssDNA-binding function although we were unable to show this directly.

Sequence and immunological characterisation of ovine pancreatic lipase

Purified ovine pancreatic lipase has been subjected to a limited protein sequence analysis. Cyanogen bromide fragments from the molecule were isolated and characterised to enable the structure of the molecule to be mapped. Some tryptic peptides were also isolated, sequenced, and aligned by homology to lipase sequences from other species. A total of 172 residues out of a possible 456 have been assigned, including 45 residues at the N-terminus and 10 residues at the C-terminus of the protein. A polyclonal antibody has been prepared to ovine lipase which has been characterised by Ouchterlony immunodiffusion and by Western blotting experiments. These experiments showed that the ovine pancreatic lipase was immunologically different from the ovine hepatic and lingual lipase, whereas there was considerable immunological similarity amongst ovine, bovine and rabbit pancreatic lipase, but less with porcine pancreatic lipase.

Ovine atrial natriuretic factor: sequence of circulating forms and metabolism in plasma

The sequence of ovine ANF is not known, yet sheep have been used extensively for ANF studies. We sequenced the circulating form of ovine ANF from coronary sinus plasma of sheep in paced heart failure. The main circulating form was identical to human ANF(99-126). Small amounts of ANF identical to human ANF(103-126) and ANF(101-126) peptides were also found. Incubation of labeled ANF in ovine serum suggested ANF(103-126) could be a degradation product of ANF(99-126). The endopeptidase-24.11 degradation product ANF(99-105/106-126) was not found in ovine plasma, in contrast to human plasma where it was a minor component. These results show that while the main circulating forms are similar in sheep and humans, there are differences in the minor peptides.

Whey proteins of the common brushtail possum (Trichosurus vulpecula): isolation, characterization and changes in concentration in milk during lactation of transferrin, alpha-lactalbumin and serum albumin

1. Transferrin and serum albumin were purified from both whey and serum and alpha-lactalbumin was purified from whey from the common brushtail possum (Trichosurus vulpecula). 2. The N-terminal amino acid sequences for transferrin and serum albumin were identical for the proteins from both whey and serum and showed homologies with transferrin or serum albumin from other species. 3. N- and C-terminal regions of possum alpha-lactalbumin were also sequenced and have been compared with wallaby alpha-lactalbumin and several eutherian alpha-lactalbumins. 4. Antisera raised to each of the three proteins were species specific and Western blots further confirmed the identity of the serum and whey transferrins and serum and whey serum albumins. 5. The concentration of transferrin increased ten-fold between days 110 and 130 of lactation, whereas no significant changes in the concentration of alpha-lactalbumin could be detected after day 60.

Isolation and structural characterization of insulin and glucagon from the holocephalan species Callorhynchus milii (elephantfish)

Both insulin and glucagon from the pancreas of the holocephalan cartilaginous fish Callorhynchus milii (elephantfish) have been isolated and purified. Two reverse-phase h.p.l.c. steps enabled recovery of sufficient material for gas-phase sequencing of the intact chains as well as peptide digestion products. The elephantfish insulin sequence shows 14 differences from pig insulin, including two unusual substitutions, Val-A14 and Gln-B30, though none of these is thought likely to influence receptor binding significantly. The insulin B-chain contains 31 residues, one more than mammalian insulins, but markedly less than that of the closely related ratfish with which it otherwise exhibits high sequence similarity. Elephantfish and pig glucagons differ at only four positions, but there are six changes from the ratfish glucagon-36 (normal glucagon contains 29 residues) sequence. It is apparent that different prohormone proteolytic processing mechanisms operate in the two holocephalan species.

Purification and sequencing of glycosylation variants of BSF-1, as a MAF, from the EL-4 leukaemia cell line

Macrophage activation activity was characterized from a PMA-induced subclone of the murine EL-4 leukaemic cell line. The MAF was purified from the cell line culture supernatant by concentration, CM-Sepharose and lentil lectin Sepharose chromatography, AcA 54 gel filtration, Mono Q FPLC and reverse phase HPLC. Four protein bands of different abundance were observed on SDS-PAGE with molecular weights of 17,500 to 21,000 Da. Three of the four proteins were sequenced from the N-terminal and shared homology with the published sequence of BSF-1. Variation of the molecular weight due to glycosylation was demonstrated by N-glycanase treatment, all four proteins gave a band of 14,200 Da after deglycosylation. Both glycosylated and deglycosylated forms of BSF-1 were equally active in the MAF assay. A monoclonal antibody to BSF-1 neutralized 80% of the activity from crude culture supernatants in the MAF assay. These studies have indicated that BSF-1 is the major, if not the only, MAF activity from this particular subline of the murine EL-4 leukaemic cell line.

Effect of extended lactation and diet on transferrin concentrations in rat milk

Milk transferrin in the rat is immunochemically identical to serum transferrin. Its concentration in milk during normal lactation (10 pups for 21 d) varies biphasically, decreasing from a value of 1.5 mg/ml in colostrum to barely detectable values at d 4 and 8 of lactation, and thereafter increasing to reach values of 4 mg/ml at d 21. The effect of extended lactation on transferrin in milk was investigated in two experiments in which litters were replaced by 4-d-old litters at d 8 and 12 of lactation or at d 20 of lactation. Transferrin concentrations in milk in both experiments increased in a similar manner to reach values of 10 mg/ml at d 28 through d 36 of lactation. Serum transferrin and serum insulin and prolactin concentrations were not significantly altered in these experiments. Premature exposure of dams to older pups did not affect the pattern of milk transferrin concentrations. Milk transferrin concentrations were, however, modulated by altering the milk demand (changing litter sizes) and by restricting either the total food intake or the protein content of the diet. These restrictions led to lower transferrin concentrations.

Isolation and characterization of fatty acid binding proteins from mammary tissue of lactating rats

A protein fraction with fatty acid binding activity has been isolated from mammary tissue from lactating rats by a process involving DEAE-cellulose ion-exchange chromatography, heat treatment, CM-cellulose ion-exchange chromatography and finally ammonium sulphate precipitation. The purified fraction migrated as a single band on SDS/polyacrylamide-gel electrophoresis with an apparent molecular mass of 14400. However, when this protein fraction was electrophoresed under non-dissociating conditions, two species were observed in a 4:1 ratio. The two components were separated using h.p.l.c. Both bind fatty acids and appear to have similar amino acid compositions although exhibiting different pI values of 4.8 and 4.9. The mammary fatty acid binding proteins appear to be very similar to the fatty acid binding protein isolated from rat heart based on the electrophoretic mobilities and amino acid composition. The major mammary form (pI 4.9) has been partially sequenced and the amino acid sequences obtained can be aligned with 67 residues of the revised rat heart amino acid sequence [Heuckeroth, Birkenmeier, Levin & Gordon (1987) J. Biol. Chem. 262, 9709-9717]. Both mammary species also showed immunochemical identity to rat heart fatty acid binding protein when tested with an anti-serum raised against the heart protein. Anti-sera raised against the minor mammary form (pI 4.8) specifically precipitated this form under non-denaturing conditions but both forms after they had been denatured. Quantitative immunoassays using the anti-(heart fatty acid binding protein) serum showed that concentrations of the fatty acid binding proteins present in mammary cytosols increase during lactation and increase further after feeding a high-fat diet.

Amino acid sequence of atrial natriuretic peptides in human coronary sinus plasma

Two atrial natriuretic peptides were purified from pooled human coronary sinus plasma by Sep-Pak extraction, immunoaffinity chromatography and reverse phase HPLC. The amino acid sequences of the two peptides were homologous with 99-126 human atrial natriuretic peptide (hANP) and 106-126 hANP, the latter being most probably linked to 99-105 ANP by the disulphide bond. The molar ratio of the peptides in plasma, as assessed by radioimmunoassay was 10:3.

Effect of dietary protein and food restriction on milk production and composition, maternal tissues and enzymes in lactating rats

Lactating rats have been fed either a protein-restricted diet (10 vs. 20% casein in the control diet) or the control diet at 80, 60 and 40% of the voluntary intake for 7 d from d 7 of lactation. Food consumption, changes in maternal live weight, litter live weight gain and the mass of several maternal tissues were determined together with the activity of several mammary and liver enzymes, including 10 that are essential for fatty acid and complex lipid synthesis. Milk production was estimated from the litter weight gain and litter weight. Lactating rats fed the 20% protein diet ad libitum consumed three times that of nonlactating rats; their liver and kidney masses were significantly higher and their adipose mass was lower. The livers of the lactating rats were fatty, containing 118 mg lipid/g compared with 42 mg/g for the nonlactating rats. Lactating rats fed either the protein-restricted diet or the control diet at 40 and 60% of the ad libitum intake of the control diet had lower mammary, liver and kidney masses than rats consuming the control diet ad libitum. Both protein and food restriction led to lower rates of milk production than those of ad libitum-fed control rats as evidenced by the decrease in litter live weight gains. The concentrations of total lipid, total protein and lactose in milk were not affected by these dietary treatments. The concentration of alpha-lactalbumin in milk of rats fed the low protein diet was, however, lower than that in the milk of all rats receiving the control diet, irrespective of intake. Consumption of the restricted diets resulted in only small changes in specific activities (mu/mg protein) of 15 mammary enzymes. In the livers, lactation led to higher specific activities of all four soluble lipogenic enzymes examined but did not affect the particulate enzymes involved in complex lipid synthesis. The dietary restrictions resulted in lower specific activities of the soluble enzymes compared with those of the lactating rats consuming the control diet ad libitum without affecting the particulate enzymes. Total activities of these enzymes were, however, lower than those for the control rats as a result of the smaller liver mass in the rats receiving the restricted diets.

The amino-acid sequences of sculpin islet somatostatin-28 and peptide YY

Two pancreatic peptides, somatostatin-28 and peptide YY, have been isolated from the Brockmann bodies of the teleost fish Cottus scorpius (daddy sculpin). Following purification by reverse-phase HPLC, each peptide was sequenced completely through to the carboxyl-terminus by gas-phase Edman degradation. Somatostatin-28 was the major form of somatostatin detected and is similar to the gene II product from anglerfish. Peptide YY (36 amino acids) more closely resembles porcine neuropeptide YY and intestinal peptide YY than it does the pancreatic polypeptides.

Protein synthesis in mammary acini isolated from lactating rats: effect of maternal diet

Protein synthesis in the rat mammary gland has been studied using acini isolated from mammary tissue by collagenase digestion. When the acini were incubated with radioactively labeled amino acids, both cellular and milk proteins were synthesized and milk proteins were secreted into the incubation medium. Antisera to the lipogenic enzyme, fatty acid synthase, and the milk proteins, alpha-lactalbumin and the caseins, raised in rabbits, were shown to be specific by analyzing immunoprecipitates on sodium dodecyl sulfate--polyacrylamide gels. The rates of synthesis and secretion of each protein by acini prepared from rats during late gestation and at specific stages of lactation reflect their previously observed concentration in the mammary gland or milk of rats at the corresponding stage of gestation or lactation. Rats were treated according to one of the following regimes between d 7 and 14 of lactation: they were fed a control (20% casein) or a low protein (10% casein) diet ad libitum, they were fed the control diet restricted to 25 g/d (40% of the voluntary intake), they were fed the control diet for 5 d and starved for 48 h or they were treated as in 3 and then refed the control diet ad libitum for 24 h. Food restriction and starvation both resulted in lowered rates of synthesis of all proteins examined compared with either the control or refed animals. Starvation also lowered the rates of secretion of the milk proteins. Consumption of the low protein diet caused a specific decrease in both the rates of synthesis and secretion of alpha-lactalbumin compared with the control rats without affecting the synthesis and secretion of the caseins.

The isolation, purification and amino-acid sequence of insulin from the teleost fish Cottus scorpius (daddy sculpin)

Insulin from the principal islets of the teleost fish, Cottus scorpius (daddy sculpin), has been isolated and sequenced. Purification involved acid/alcohol extraction, gel filtration, and reverse-phase high-performance liquid chromatography to yield nearly 1 mg pure insulin/g wet weight islet tissue. Biological potency was estimated as 40% compared to porcine insulin. The sculpin insulin crystallised in the absence of zinc ions although zinc is known to be present in the islets in significant amounts. Two other hormones, glucagon and pancreatic polypeptide, were copurified with the insulin, and an N-terminal sequence for pancreatic polypeptide was determined. The primary structure of sculpin insulin shows a number of sequence changes unique so far amongst teleost fish. These changes occur at A14 (Arg), A15 (Val), and B2 (Asp). The B chain contains 29 amino acids and there is no N-terminal extension as seen with several other fish. Presumably as a result of the amino acid substitutions, sculpin insulin does not readily form crystals containing zinc-insulin hexamers, despite the presence of the coordinating B10 His.

Milk composition of rats feeding restricted litters

Milk samples were taken from rats feeding ten pups and from both the suckled and non-suckled glands of rats feeding two pups. The lipid, protein and lactose concentrations were similar in the milks from the secreting glands, but the fluid from the non-suckled glands contained less lactose and lipid but significantly higher total protein and transferrin concentrations. The fatty acid compositions of the milk from the three sources were very similar. The mammary tissue from the rats feeding ten pups had a higher DNA content/g wet wt. than either the suckled or non-suckled mammary tissue of the rats feeding two pups. The specific activities of several lipogenic enzymes were significantly lower in the non-suckled mammary tissue.

Amino acid sequence of ovine 6-phosphogluconate dehydrogenase

The amino acid sequence of the NADP+-dependent enzyme ovine 6-phosphogluconate dehydrogenase has been determined by conventional direct protein sequence analysis of peptides resulting from digestion of the protein with trypsin and chemical cleavages with cyanogen bromide, hydroxylamine, and iodosobenzoic acid. The polypeptide contains 466 amino acids and its NH2 terminus is acetylated. The Candida utilis enzyme is inactivated by reaction of pyridoxal phosphate with two lysine residues (Minchiotti, L., Ronchi, S., and Rippa, M. (1981) Biochim. Biophys. Acta 657, 232-242). These residues are conserved in the ovine enzyme. In contrast to NAD+ dehydrogenases which have weakly related sequences and spatially related folds in their nucleotide-binding sites, no significant sequence homologies were detected between 6-phosphogluconate dehydrogenase and any of three other NADP+-requiring enzymes, glutamate dehydrogenase, p-hydroxybenzoate hydroxylase, and dihydrofolate reductase. This is in accord with structural data that show no spatial relationship between NADP+-binding sites in these enzymes.

The three dimensional structure of sheep liver 6-phosphogluconate dehydrogenase at 2.6 A resolution

The three-dimensional structure of sheep liver 6-phosphogluconate dehydrogenase has been determined at 2.6 A resolution by X-ray crystallographic studies. The amino acid sequence of the enzyme is now known and can be fitted to a modified electron density map. Use of 6 A electron density maps and the results of chemical modification experiments allows description of the active site and identification of residues which may be implicated in the binding of co-enzyme and substrate.

Solid-phase sequence analysis of polypeptides eluted from polyacrylamide gels. An aid to interpretation of DNA sequences exemplified by the Escherichia coli unc operon and bacteriophage lambda

An approach to sequencing proteins by the solid-phase method combined with isolation of proteins and polypeptides by gel electrophoresis is described. Mixtures of proteins or polypeptides resulting from digests are fractionated in the presence of dodecylsulphate in polyacrylamide gels. They are detected with Coomassie blue, eluted, selectively reacted with porous glass derivatives and sequenced in their amino-terminal regions with the aid of a new microsequencer. Alternatively they can be analysed or digested with enzymes and fingerprinted. It is a relatively rapid method of purifying proteins for sequence analysis which we have used to provide partial protein sequence data to complement DNA sequences. Nine genes, four from the unc operon of Escherichia coli encoding the alpha, beta, gamma and epsilon subunits of ATP synthase and five for capsid proteins of bacteriophage lambda, have been identified by this method.

The amino acid sequence of the tryptic peptides from actinidin, a proteolytic enzyme from the fruit of Actinidia chinensis

The amino acid sequences of the tryptic peptides of the thiol proteinase actinidin from Actinidia chinensis were determined by the manual dansyl--Edman procedure. There are 12 tryptic peptides, which give a polypeptide chain of 220 residues with a mol.wt. of 23500. An alignment of the tryptic peptides was made by using the X-ray-crystallographic data of Baker [(1977) J. Mol. Biol. 115, 263--277] determined at 0.28 nm resolution on crystalline actinidin. Detailed evidence for the amino acid sequences of the tryptic peptides has been deposited as Supplementary Publication SUP 50083 (14 pages) at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1978) 169, 5.