Isolation and characterization of a D-7 LEA protein from pollen that stabilizes glasses in vitro

A heat-soluble protein present in substantial quantities in Typha latifolia pollen was purified to homogeneity. The protein was subjected to cyanogen bromide cleavage, and the peptides produced were separated by HPLC chromatography and sequenced. The two sequences determined were found to be related to the putative D76 LEA protein from Brassica napus seeds and one of them to the D-7 LEA protein from upland cotton. This suggests the pollen protein to be a member of the LEA group III family of proteins. The secondary structure of the protein in solution and in the dry state was investigated using Fourier transform IR spectroscopy. Whereas the protein in solution was highly unordered, being largely in a random coil conformation, the conformation was largely alpha-helical after fast drying. Slow drying reversibly led to both alpha-helical and intermolecular extended beta-sheet structures. When dried in the presence of sucrose, the protein adopted alpha-helical conformation, irrespective of drying rate. The effect of the protein on the stability of sucrose glasses was also investigated. The dehydrated mixture of sucrose and the LEA protein had higher glass transition temperatures and average strength of hydrogen bonding than dehydrated sucrose alone. We suggest that LEA proteins may play a role together with sugars in the formation of a tight hydrogen bonding network in the dehydrating cytoplasm, thus conferring long-term stability.

Shedding of somatic angiotensin-converting enzyme (ACE) is inefficient compared with testis ACE despite cleavage at identical stalk sites

The somatic and testis isoforms of angiotensin-converting enzyme (ACE) are both C-terminally anchored ectoproteins that are shed by an unidentified secretase. Although testis and somatic ACE both share the same stalk and membrane domains the latter was reported to be shed inefficiently compared with testis ACE, and this was ascribed to cleavage at an alternative site [Beldent, Michaud, Bonnefoy, Chauvet and Corvol (1995) J. Biol. Chem. 270, 28962-28969]. These differences constitute a useful model system of the regulation and substrate preferences of the ACE secretase, and hence we investigated this further. In transfected Chinese hamster ovary cells, human somatic ACE (hsACE) was indeed shed less efficiently than human testis ACE, and shedding of somatic ACE responded poorly to phorbol ester activation. However, using several analytical techniques, we found no evidence that the somatic ACE cleavage site differed from that characterized in testis ACE. First, anti-peptide antibodies raised to specific sequences on either side of the reported cleavage site (Arg(1137)/Leu(1138)) clearly recognized soluble porcine somatic ACE, indicating that cleavage was C-terminal to Arg(1137). Second, a competitive ELISA gave superimposable curves for porcine plasma ACE, secretase-cleaved porcine somatic ACE (eACE), and trypsin-cleaved ACE, suggesting similar C-terminal sequences. Third, mass-spectral analyses of digests of released soluble hsACE or of eACE enabled precise assignments of the C-termini, in each case to Arg(1203). These data indicated that soluble human and porcine somatic ACE, whether generated in vivo or in vitro, have C-termini consistent with cleavage at a single site, the Arg(1203)/Ser(1204) bond, identical with the Arg(627)/Ser(628) site in testis ACE. In conclusion, the inefficient release of somatic ACE is not due to cleavage at an alternative stalk site, but instead supports the hypothesis that the testis ACE ectodomain contains a motif that activates shedding, which is occluded by the additional domain found in somatic ACE.

Modulation of juxtamembrane cleavage ("shedding") of angiotensin-converting enzyme by stalk glycosylation: evidence for an alternative shedding protease

The role of juxtamembrane stalk glycosylation in modulating stalk cleavage and shedding of membrane proteins remains unresolved, despite reports that proteins expressed in glycosylation-deficient cells undergo accelerated proteolysis. We have constructed stalk glycosylation mutants of angiotensin-converting enzyme (ACE), a type I ectoprotein that is vigorously shed when expressed in Chinese hamster ovary cells. Surprisingly, stalk glycosylation did not significantly inhibit release. Introduction of an N-linked glycan directly adjacent to the native stalk cleavage site resulted in a 13-residue, proximal displacement of the cleavage site, from the Arg-626/Ser-627 to the Phe-640/Leu-641 bond. Substitution of the wild-type stalk with a Ser-/Thr-rich sequence known to be heavily O-glycosylated produced a mutant (ACE-JGL) in which this chimeric stalk was partially O-glycosylated; incomplete glycosylation may have been due to membrane proximity. Relative to levels of cell-associated ACE-JGL, rates of basal, unstimulated release of ACE-JGL were enhanced compared with wild-type ACE. ACE-JGL was cleaved at an Ala/Thr bond, 14 residues from the membrane. Notably, phorbol ester stimulation and TAPI (a peptide hydroxamate) inhibition of release-universal characteristics of regulated ectodomain shedding-were significantly blunted for ACE-JGL, as was a formerly undescribed transient stimulation of ACE release by 3, 4-dichloroisocoumarin. These data indicate that (1) stalk glycosylation modulates but does not inhibit ectodomain shedding; and (2) a Ser-/Thr-rich, O-glycosylated stalk directs cleavage, at least in part, by an alternative shedding protease, which may resemble an activity recently described in TNF-alpha convertase null cells [Buxbaum, J. D., et al. (1998) J. Biol. Chem. 273, 27765-27767].

Inclusion of polyvinylpyrrolidone in the polymerase chain reaction reverses the inhibitory effects of polyphenolic contamination of RNA

Polysaccharides, secondary metabolites and poly-phenolics are known to co-isolate with nucleic acids from plant tissues resulting in inhibition of molecular manipulations. RNA isolated from the polyphenolic-rich resurrection plant, Myrothamnus flabellifolius, was demonstrated to inhibit a standard polymerase chain reaction used as an assay despite the inclusion of the polyphenolic-binding compound poly(1-vinylpyrrolidone-2) (PVP) into the RNA isolation medium. This inhibition was, however, reversed by the addition of PVP into the PCR mixture itself. Confirmation of the inhibitory effect of polyphenolics on PCR was obtained by addition of green tea polyphenolics to the standard PCR assay. This inhibition was also reversed by the simultaneous inclusion of PVP.

Phorbol ester-induced juxtamembrane cleavage of angiotensin-converting enzyme is not inhibited by a stalk containing intrachain disulfides

Specialized proteases, referred to as sheddases, secretases, or membrane-protein-solubilizing proteases (MPSPs), solubilize the extracellular domains of diverse membrane proteins by catalyzing a specific cleavage in the juxtamembrane stalk regions of such proteins. A representative MPSP (tumor necrosis factor-alpha convertase) was cloned recently and shown to be a disintegrin metalloprotease that is inhibited by peptide hydroxamates including the compound TAPI. Substrate determinants that specify cleavage by MPSPs remain incompletely characterized, but may include the physicochemical properties of the stalk or unidentified recognition motifs in the stalk or the extracellular domain. We constructed a mutant angiotensin-converting enzyme (ACE) in which the stalk has been replaced with an epidermal growth factor (EGF)-like domain (ACE-JMEGF), to test the hypothesis that MPSP cleavage requires an open, comparatively unfolded or extended stalk. Wild-type ACE is a type I transmembrane (TM) ectoprotein that is efficiently solubilized by a typical MPSP activity. We found that ACE-JMEGF was solubilized inefficiently and accumulated in a cell-associated form on transfected Chinese hamster ovary (CHO) cells; cleavage was stimulated by phorbol ester and inhibited by TAPI, features typical of MPSP activity. Determination of the C-terminus of soluble ACE-JMEGF revealed that, surprisingly, cleavage occurred at a Gly-Phe bond between the fifth and sixth cysteines within the third disulfide loop of the EGF-like domain. Reduction of intact CHO cells with tributylphosphine resulted in the rapid release of ACE-JMEGF (but not wild-type ACE) into the medium, suggesting that a proportion of membrane-bound ACE-JMEGF is cleaved but remains cell-associated via disulfide tethering. The mechanism for the release of ACE-JMEGF in the absence of chemical reduction is unclear. We conclude that the presence of a compact, disulfide-bridged domain does not per se inhibit cleavage by an MPSP activity, but ectodomain release is prevented by disulfide tethering to the TM domain.

Isolation and amino acid sequence analysis reveal an ancient evolutionary origin of the cleavage stage (CS) histones of the sea urchin

The cleavage stage (CS) H1, H2A, and H2B histones of the sea urchin, which have previously been identified by their distinct electrophoretic mobility on Triton/acid/urea gels, are known to be maternally expressed during oogenesis and have been implicated in chromatin remodeling of the male pronucleus following fertilization. Here, we describe the isolation of these three CS histones by reverse-phase HPLC chromatography. Moreover, a novel CS H3 protein was identified by the same purification procedure. A low incorporation of radioactive amino acids into the CS histones during early development revealed that the bulk of these proteins in the blastula embryo are derived from the maternal pool of the egg. Amino acid analysis, together with the previously described electrophoretic mobilities, unequivocally identified the purified proteins as CS histones. Peptide sequence analysis confirmed the novel nature of the CS variants as they are distantly related to the early, late, and sperm histone subtypes of the sea urchin. The CS H1 protein displays highest sequence similarity with the H1M (B4) histone of Xenopus laevis, indicating that the frog H1M protein may be a vertebrate homologue of the CS H1 histone. These data suggest an ancient evolutionary origin and wide distribution of the CS histone variants.

Proteolytic release of membrane proteins: studies on a membrane-protein-solubilizing activity in CHO cells

Diverse membrane proteins are solubilized by a specific proteolytic cleavage in the stalk sequence adjacent to the membrane anchor, with release of the extracellular domain. Examples are the amyloid precursor protein, membrane-bound growth factors and angiotensin-converting enzyme (ACE). The identities and characteristics of the responsible proteases remain elusive. We have studied this process in Chinese hamster ovary (CHO) cells stably expressing wild-type ACE (WT-ACE) or juxtamembrane (stalk) deletion or chimaera mutants. Determination of the C termini (i.e. the cleavage sites) of released, soluble wild-type and mutant ACE by MALDI-TOF mass spectrometry indicated that the membrane-protein-solubilizing protease (MPSP) in CHO cells is not constrained by a particular cleavage site motif or by a specific distance from the membrane, but instead may position itself with respect to the putative proximal, folded extracellular domain adjacent to the stalk. Nevertheless, kinetic analyses of release rates indicated that a minimum distance from the membrane must be preserved. Interestingly, soluble full-length (anchor-plus) WT-ACE incubated with fractions of, or intact, CHO cells was not cleaved. In all cases, release was stimulated by a media change or by the addition of phorbol ester, with rate enhancements of 5- and 50-fold, respectively, for WT-ACE. The phorbol ester effect was abolished by staurosporine, a protein kinase C (PKC) inhibitor. We propose that the CHO cell MPSP that solubilizes ACE: (1) only cleaves proteins embedded in a membrane; (2) requires an accessible stalk and cleaves at a minimum distance from both the membrane and proximal extracellular domain; (3) positions itself primarily with respect to the proximal extracellular domain and (4) is regulated in part by a PKC-dependent mechanism.

The five cleavage-stage (CS) histones of the sea urchin are encoded by a maternally expressed family of replacement histone genes: functional equivalence of the CS H1 and frog H1M (B4) proteins

The cleavage-stage (CS) histones of the sea urchin are known to be maternally expressed in the egg, have been implicated in chromatin remodeling of the male pronucleus following fertilization, and are the only histone variants present in embryonic chromatin up to the four-cell stage. With the help of partial peptide sequence information, we have isolated and identified CS H1, H2A, H2B, H3, and H4 cDNAs from egg poly(A)+ mRNA of the sea urchin Psammechinus miliaris. All five CS proteins correspond to replacement histone variants which are encoded by replication-independent genes containing introns, poly(A) addition signals, and long nontranslated sequences. Transcripts of the CS histone genes could be detected only during oogenesis and in development up to the early blastula stage. The CS proteins, with the exception of H4, are unique histones which are distantly related in sequence to the early, late, and sperm histone subtypes of the sea urchin. In contrast, the CS H1 protein displays highest sequence homology with the H1M (B4) histone of Xenopus laevis. Both H1 proteins are replacement histone variants with very similar developmental expression profiles in their respective species, thus indicating that the frog H1M (B4) gene is a vertebrate homolog of the CS H1 gene. These data furthermore suggest that the CS histones are of ancient evolutionary origin and may perform similar conserved functions during oogenesis and early development in different species.

Proteolytic release of membrane-bound angiotensin-converting enzyme: role of the juxtamembrane stalk sequence

Many structurally and functionally diverse membrane proteins are solubilized by a specific proteolytic cleavage in the stalk sequence adjacent to the membrane anchor, with release of the extracellular domain. Examples are the amyloid precursor protein, membrane-bound growth factors, and angiotensin-converting enzyme (ACE). The identities and characteristics of the responsible proteases remain elusive. We have studied this process in Chinese hamster ovary (CHO) cells stably expressing wild-type ACE (WT-ACE; human testis isozyme) or one of four juxtamembrane (stalk) mutants containing either deletions of 17, 24, and 47 residues (ACE-JM delta 17, -JM delta 24, and -JM delta 47, respectively) or a substitution of 26 stalk residues with a 20-residue sequence from the stalk of the low-density lipoprotein receptor (ACE-JMLDL). The C termini of released, soluble WT-ACE and ACE-JM delta 17 and -JMLDL were determined by MALDI-TOF mass spectrometry analyses of C-terminal peptides generated by CNBr cleavage. Observed masses of 4264 (WT-ACE) and 4269 (ACE-JM delta 17) are in good agreement with an expected mass of 4262 for the C-terminal CNBr peptide ending at Arg-627, indicating cleavage at the Arg-627/Ser-628 bond in both WT-ACE and ACE-JM delta 17, at distances of 24 and 10 residues from the membrane, respectively. Data for ACE-JM delta 24 are also consistent with cleavage at or near Arg-627. For ACE-JMLDL, in which the native cleavage site is absent, observed masses of 4372 and 4542 are in close agreement with expected masses of 4371 and 4542 for peptides ending at Ala-628 and Gly-630, respectively, indicating cleavages at 17 or 15 residues from the membrane. These data indicate that the membrane-protein-solubilizing protease (MPSP) in CHO cells is not constrained by a particular cleavage site motif or by a specific distance from the membrane but instead may position itself with respect to the putative proximal, folded extracellular domain adjacent to the stalk. Nevertheless, cleavage at a distance of 10 residues from the membrane is more favorable, as ACE-JM delta 17 is cleaved 12-fold faster than WT-ACE. In contrast, ACE-JM delta 24 is released 17-fold slower, suggesting that a minimum distance from the membrane must be preserved. This is supported by results with the ACE-JM delta 47 mutant, which is membrane-bound but not cleaved, likely because the entire stalk has been deleted. Finally, soluble full-length (anchor-plus) WT-ACE is not cleaved when incubated with various CHO cell fractions or intact CHO cells. On the basis of these and other data, we propose that the CHO cell MPSP that solubilizes ACE (1) only cleaves proteins embedded in a membrane; (2) requires an accessible stalk and cleaves at a minimum distance from both the membrane and proximal extracellular domain; (3) positions itself primarily with respect to the proximal extracellular domain; and (4) may have a weak preference for cleavage at Arg/Lys-X bonds.

Derivatization of polyvinylidene difluoride membranes for the solid-phase sequence analysis of a phosphorylated sea urchin embryo histone H1 peptide

We describe a simple and effective chemical protocol for attaching polyallylamine to polyvinylidene difluoride (PVDF) membranes. The underivatized PVDF discs were first etched in 0.5 M alcoholic KOH for 1.5 min and subsequently reacted with polyallylamine of high molecular weight under alkaline conditions. The covalently attached amino groups were reacted with 1,4-phenylene diisothiocyanate (DITC), thus converting the amino-modified PVDF discs to DITC-functionalized discs. The substitution level of the DITC-functionalized discs was found to be lower than that of the equivalent discs available commercially. Lysine-containing polypeptides were immobilized on these DITC-membrane discs and then subjected to either solid-phase manual Edman degradation or automated gas-phase sequencing. The method was found to be well suited for the sequencing of 32P-labeled phosphopeptides by employing the manual solid-phase technique.

Bitis arietans nerve growth factor is a disulphide-linked homodimer

1. Nerve growth factor from Bitis arietans venom was isolated in high yield and purified to homogeneity using a rapid two-step procedure involving gel exclusion chromatography and reversed-phase HPLC. 2. On polyacrylamide gel electrophoresis in SDS, the NGF migrates as a 25 kDa homodimer and is thus atypical of other Viperid NGFs. 3. Evidence suggests that, unlike mammalian beta NGFs, the subunits of the Bitis arietans homodimer are covalently linked by a disulphide bond(s). 4. Partial sequence analysis shows that only 6 out of the first 21 amino acids are identical with those of cobra NGF including cys-14 and val-21 which are known to be important for NGF activity.

Total solid-phase synthesis and prolactin-inhibiting activity of the gonadotropin-releasing hormone precursor protein and the gonadotropin-releasing hormone associated peptide

The human gonadotropin-releasing hormone precursor protein, pHGnRH (Met-23-Ile69) (preproGnRH), and three of its fragment peptides, pHGnRH (Asp14-Ile69) (gonadotropin-releasing hormone associated peptide--GAP), pHGnRH (Phe38-Ile69), and pHGnRH (Ser47-Ile69), were assembled in a stepwise solid-phase cosynthesis employing Boc/Bzl tactics and an optimized acylation schedule which included recoupling steps with hexafluoro-2-propanol to help overcome the aggregation of the pendant peptide chains of the peptidoresin during difficult couplings. Reversed-phase high-performance liquid chromatography (HPLC) purification yielded products which were characterized by analytical reversed-phase HPLC, ion-exchange chromatography, capillary zone electrophoresis, SDS-polyacrylamide gel electrophoresis, and ion-spray mass spectrometry to reveal a high degree of homogeneity. Biological characterization demonstrated that only GAP stimulated luteinizing hormone and follicle-stimulating hormone release from primary cultures of rat anterior pituitary cells, while GAP, pHGnRH (Phe38-Ile69), and preproGnRH all inhibited prolactin release, with the latter being the most potent at concentrations comparable to bromocryptine. However, only GAP and pHGnRH (Phe38-Ile69) were able to displace a labeled gonadotropin-releasing hormone agonist from binding to rat pituitary membrane preparations. This first demonstration of significant biological activity with a precursor protein also suggests that the gonadotropin-releasing and prolactin release-inhibiting functions of GAP are not mediated through the same pituitary receptors.

Pheromones of the Scarabaeinae, II*. Composition of the Pheromone Disseminating Carrier Material Secreted by Male Dung Beetles of the Genus Kheper

Gel electrophoresis of the white flocculcnt phcromonc disseminating secretions produced by males of the three dung beetle species, Kheper lamarcki, K. nigroaeneus and K. subaeneus, revealed that three different proteins with molecular masses of ca. 15 kDa are the major constitu- ents of these secretions. The molecular mass of these components in the secretions of K. lamarcki and K. nigroaeneus was determined more accurately by 252Cf plasma desorption mass spectrometry to be 15451 ± 10 and 15477 ± 10 Da respectively. The N-terminal amino acids in the major proteinaceous component of the secretions revealed similarities as well as differences in the primary structures of the proteins secreted by the three species. The amino acid composition of the secretions of the three species is closely related. Due to the presence of large amounts of aspartic and glutamic acid, and small amounts of the basic amino acids, the pro- teinaceous component of the carrier material is expected to have a low isoelectric point which, together with the presence of large amounts of the hydrophobic amino acids, may impart properties that are to be expected for a carrier material which is used for the dissemination of inter alia long-chain fatty acids and their esters. Exposure of bovine pancreas trypsin, bovine albumin and the carrier protein of K. lamarcki to the vapour of 2,6-dimcthyl-5-hcptcnoic acid, the major volatile constituent with electro- antennogram activity in the secretion of this species, followed by quantitative determination of the acid adsorbed on these proteins, showed that albumin and the carrier protein have an approximately equal affinity for the acid, whereas trypsin retained only about one third of the amount of the acid adsorbed on the other two proteins. It was concluded that albumin should be a suitable substitute for the carrier protein in field tests with synthetic constituents of the abdominal secretion of these insects.

Human serum amyloid A protein. The assignment of the six major isoforms to three published gene sequences and evidence for two genetic loci

Serum amyloid A protein (apo-SAA) is an acute-phase reactant and an apolipoprotein of high density lipoproteins (HDL). Six major isoforms of apo-SAA occur in humans (pI 6.0, 6.4, 7.0, 7.4, 7.5, 8.0). In this report we have rationalized the phenotypic expression of apo-SAA isoforms with published apo-SAA structures predicted from apo-SAA cDNA's pA1 and pSAA82 and the genomic DNA SAAg9. The six apo-SAA isoforms fall into three pairs, pI 6.0/6.4, 7.0/7.5, and 7.4/8.0, which are products of cDNA pA1, cDNA pSAA82, and genomic DNA SAAg9, respectively. The second of each isoform pair (i.e. pI 6.4, 7.5, and 8.0) is the "primary" product: a 104-residue peptide with the NH2-terminal sequence Arg-Ser-Phe-Phe. Each primary product is processed either to a major 103-residue peptide with the NH2-terminal sequence Ser-Phe-Phe or processed to a minor 102-residue product which results from the loss of both an Arg and a Ser residue from the NH2 termini. These "secondary" products have the lower pI values of 6.0, 7.0, and 7.4, respectively. The isoelectric points of the SAAg9 products were confirmed by expression of SAAg9 in transfected mouse L-cells. Both the pI 8.0 and 7.4 isoforms were present in cellular extracts, suggesting that post-translational modification of apo-SAA may occur intracellularly. However, the greater relative abundance of the pI 7.4 isoform extracellularly suggests that the major conversion may occur after secretion. Whereas the gene corresponding to the pA1 cDNA sequence does not show allelic variation, the segregation characteristics of the pI 7.0/7.5 and 7.4/8.0 isoform pairs amongst individuals suggests that these isoforms are the products of genes (with sequences corresponding to pSAA82 and SAAg9, respectively) which are allelic variants at a single locus distinct from that for the pI 6.0/6.4 isoform pair.

The primary structure of the histone H2A(2) type from wheat germ. A core histone type with both, N-terminal and C-terminal extensions

The histone H2A(2) type from wheat germ comprises at least two highly homologous isohistones with 151 amino acid residues. Microheterogeneity occurs mainly at the N-terminal and C-terminal regions. These isohistones have both N-terminal (7 amino acid residues) and C-terminal (15 amino acid residues) extensions relative to calf thymus histone H2A.

The amino acid sequence of wheat histone H2B(2). A core histone with a novel repetitive N-terminal extension

Two of the four electrophoretic histone H2B variants present in wheat embryos have been isolated. The complete primary structure of the H2B(2) variant has been deduced from sets of overlapping peptides generated by CNBr cleavage, Staphylococcus aureus V8 protease, endoproteinase Arg-C, the post-proline cleaving enzyme, chymotrypsin and cleavage in dilute acid. A minimum of 17 peptides were required to establish the sequence. This variant has a blocked N terminus and comprises a total of 149 amino acids. The C-terminal two-thirds of the protein are highly homologous to vertebrate H2B. In contrast, the N-terminal third is entirely different and contains an N-terminal extension of 23 residues in which the sequence Ala-Glu-Lys or variants are repeated several times. This region is also highly homologous to the H2B from Tetrahymena pyriformis. It shows in addition similarities to wheat H2A(1) and bovine H1.

The primary structure of histone H3 from wheat

Wheat embryo histone H3 has been isolated and purified and the elucidation of the complete amino-acid sequence is described. Peptides were generated by cleavages with CNBr, S. aureus V8 proteinase, endoproteinase Lys-C and trypsin. The peptides were purified by HPLC and the sequence determined by solid-state and gas-phase sequencing methodology. The amino-acid sequence of the protein is identical to pea embryo histone H3 and the sequence deduced from the nucleotide sequence of a wheat embryo histone gene (Tabata T. et al. (1984) Mol. Gen. Genet. 196, 397-400).

Manual gas-phase isothiocyanate degradation

We describe a manual gas-phase isothiocyanate degradation procedure for the primary structure determination of proteins and peptides. The proteins and peptides are applied to a polybrene-coated glass fiber filter wedged into a small glass column. The phenylisothiocyanate is directly pipetted onto the filter disk. The coupling and cleavage reactions are performed in small desiccators containing trimethylamine and trifluoroacetic acid vapors, respectively. The wash and extraction steps are performed by allowing the suitable solvents to percolate through the filter disk. The extracted anilinothiazolinone is then converted to the phenylthiohydantoin and identified by any one of a number of described methods. Our results show that this method is very sensitive and that the reactions proceed faster than those of the published automated procedure. No expensive equipment is required and the manual degradation can be performed by a laboratory assistant. A large number of samples can be simultaneously subjected to the degradation under identical conditions, making this an ideal method for physicochemical investigations into the isothiocyanate degradation. We also use this method to screen HPLC fractions after enzymatic protein fragmentation. Manually sequenced glass filters can be transferred to the automated instrument for more extended degradations.

Mr determination of histones from their electrophoretic mobility in acidic urea gels in the absence of detergents

The Mr of histones can be determined from their electrophoretic mobility at pH 2.3, 8 M urea in a polyacrylamide gel by correcting for differences in their charge density and properties of the gel matrix. The applicability of this method to other proteins is considered.

The amino acid sequence of wheat histone H2A(1). A core histone with a C-terminal extension

The complete amino acid sequence (145 residues) of histone variant H2A(1) from wheat germ Triticum aestivum cultivar T4 has been established from Edman degradation of large overlapping fragments. The sequence of histone variant H2A(1) differs from the homologous calf histone in 61 amino acid positions. These differences include an extension of H2A(1) by 19 amino acids at its carboxyl end.

The identification by sequence homology of stage-specific sea urchin embryo histones H1

The histone H1 fraction from gastrula of the sea urchin Parechinus angulosus consists of a multitude of polypeptides with different electrophoretic mobilities. The synthesis of these proteins is programmed. Amino acid composition, electrophoretic properties and sequence homologies identify these as isohistones H1. One of these isohistones atypically binds the non-ionic detergent Triton X-100.

The histones of yeast. The isolation and partial structure of the core histones

The four core histones of yeast chromatin have been isolated. Amino acid composition, electrophoretic mobility and partial sequences identify one variant each of the histones H3 and H4, whereas the histones H2A and H2B are represented by two variants each. In the yeast histones H3 and H4 7% of the residues, positioned in the partial sequences vary if compared with the corresponding histones from higher plants and animals, for the histones H2A and H2B from yeast this figure is 20%.

The primary structure of histone H1 from sperm of the sea urchin Parechinus angulosus. 2. Sequence of the C-terminal CNBr peptide and the entire primary structure

The primary structure of sperm histone H1Parechinus has been determined. H1Parechinus consists of a polypeptide chain of the following 248 amino acid residues: Pro-Gly-Ser-Pro-Gln-Lys-Arg-Ala-Ala-Ser-Pro-Arg-Lys-Ser-Pro-Arg-Lys-Ser-Pro-Lys-Lys-Ser-Pro-Arg-Lys-Ala-Ser-Ala-Ser-Pro-Arg-Arg-Lys-Ala-Lys-Arg-Ala-Arg-Ala-Ser-Thr-His-Pro-Pro-Val-Leu-Glu-Met-Val-Gln-Ala-Ala-Ile-Thr-Ala-Met-Lys-Glu-Arg-Lys-Gly-Ser-Ser-Ala-Ala-Lys-Ile-Lys-Ser-Tyr-Met-Ala-Ala-Asn-Tyr-Arg-Val-Asp-Met-Asn-Val-Leu-Ala-Pro-His-Val-Arg-Arg-Ala-Leu-Arg-Asn-Gly-Val-Ala-Ser-Gly-Ala-Leu-Lys-Gln-Val-Thr-Gly-Thr-Gly-Ala-Ser-Gly-Arg-Phe-Arg-Val-Gly-Ala-Val-Ala-Lys-Pro-Lys-Lys-Ala-Lys-Lys-Thr-Ser-Ala-Ala-Ala-Lys-Ala-Lys-Lys-Ala-Lys-Ala-Ala-Ala-Ala-Lys-Lys-Ala-Arg-Arg-leads to Lys-Ala-Lys-Ala-Ala-Ala-Lys-Arg-Lys-Ala-Ala-Leu-Ala-Lys-Lys-Lys-Ala-Ala-Ala-Ala-Lys-Arg-Lys-Ala-Ala-Ala-Lys-Ala-Lys-Lys-Ala-Lys-Lys-Pro-Lys-Lys-Lys-Ala-Ala-Ala-Lys-Lys-Ala-Lys-Lys-Pro-Ala-Lys-Lys-Ser-Pro-Lys-Lys-Ala-Lys-Lys-Pro-Ala-Lys-Lys-Ser-Pro-Lys-Lys-Lys-Lys-Ala-Lys-Arg-Ser-Pro-Lys-Lys-Ala-Lys-Lys-Ala-Ala-Gly-Lys-Arg-Lys-Pro-Ala-Ala-Lys-Lys-Ala-Arg-Arg-Ser-Pro-Arg-Lys-Ala-Gly-Lys-Arg-Arg-Ser-Pro-Lys-Lys-Ala-Arg-Lys. The protein consists of three domains. Compared to other H1 and H5 histones, there is a very similar hydrophobic central domain and the carboxyl-terminal domain is very rich in lysine and alanine. H1Parechinus is similar to H5 histones in that the carboxyl-terminal domain also contains many arginine residues close to the carboxyl terminus. The carboxyl-terminal domain of H1Parechinus appears to have been constructed by a series of variable duplications. The amino-terminal domain of H1Parechinus is longer and quire different to that of other H1 and H5 histones and is characterized by a repeating tetrapeptide of the general type Ser-Pro-(basic)2. The known sequence of a histone H1 gene from Psammechinus miliaris [Schaffner, W. et al. (1978) Cell, 14, 655-671] is compared to the sequence of H1Parechinus. Again the central hydrophobic domains are similar whereas the amino terminal domains are very different. The functions of the various domains of sperm histone H1Parechinus are discussed.

Nature and extent of peptide bond cleavage by anhydrous heptafluorobutyric acid during Edman degradation

It is well established that during the isothiocyanate degradation of proteins a gradual increase of the level of all thiohydantoin derivatives of amino acids occurs, which progressively obscures the sequential identification of the significant N-terminal amino acids. The major cause for this has been shown to be due to a hitherto unknown specific cleavage at aspartic acid residues in anhydrous heptafluorobutyric acid and to a lesser extent, the N leads to O shift in peptide bonds involving hydroxyamino acids. Measures to reduce the susceptibility of the peptide bonds at these sites are described.

Plant histone 2 from wheat germ, a family of histone H2a variants. Partial amino acid sequences

1. The 0.5 M perchloric acid extract prepared from chromatin of wheat germ, Triticum aestivum, contains a group of histones formerly called plant histones. These can be resolved by gel filtration on Bio-Gel P-60 with subsequent CM-cellulose ion-exchange chromatography into five histone fractions containing families of histones H2A and H2B. 2. The partial amino acid sequences of histone H2A variants H2A(1)Triticum, H2A(2)Triticum and H2A(3)Triticum are presented. Extensive sequence homology exists between calf thymus histone H2A and wheat embryo H2A histones. Differences are largely due to conservative amino acid substitutions and in two of the variants, viz. H2A(2) and H2A(3) to N-terminal extensions of the polypeptide chains.

A histone programme during the life cycle of the sea urchin

The histone complement of chromatin from early gastrula, late gastrula and from fully differentiated gut cells of the sea urchin Parechinus angulosus has been fractionated by molecular sieve and ion-exchange chromatography. Several of the subfractions thus isolated have been characterized by amino acid composition and partial amino acid sequences as a series of variants of the histones H1, H2A and H2B. Specific histone variants are present in chromatin at specific stages of differentiation.

The complete amino-acid sequence of histone H2B from the mollusc Patella granatina

1. From the marine mollusc, Patella granatina, a histone has been isolated. Its primary structure has been established and it has been designated histone H2Bpatella. It consists of a polypeptide chain of 121 amino acids. 2. In the carboxy-terminal two thirds of the molecule there is a highly degree of sequence homology to the corresponding region in calf histone H2B with identical residues in 95% of the positions. 3. In the N-terminal 22 amino acids histone H2Bpatella differs considerably from the mammalian histone H2B and it is shorter by four residues.

A histone H2B variant from the embryo of the sea urchin Parenchinus angulosus

A variant of histone H2B has been isolated from sea urchin embryo (Parenchinus angulosus). Out of the 53 amino acids positioned in the three CNBr-peptides only 26 residues are identical to those in the corresponding positions of calf thymus histone H2B. A similar degree of homology exists between the embryonic variant and the previously characterized variants from sperm cells of the same organism.

The partial amino acid sequences of the two H2B histones from sperm of the sea urchin Psammechinus miliaris

Two new histone H2B variants have been isolated from sperm cells of the sea urchin Psammechinus miliaris. They have been designated sperm histone H2B(1) Psammechinus and sperm histone H2B(2) Psammechinus. Both histones are highly homologous to the previously described sperm histones from Parechinus angulosus (Strickland et al. (1977) Eur. J. Biochem. 77, 263--275 and 277--286). The amino acid sequences of the Ps. miliaris sperm histones, though highly homologous, are not identical to the amino acid sequence derived from the codon sequence of a histone H2B gene, characterized from the same organism by Birnstiel et al. ((1977) Nature 266, 603--607).

The complete amino-acid sequence of histone H2B(3) from sperm of the sea urchin Parechinus angulosus

The primary structure of a third H2B histone isolated from sperm of the sea urchin Parechinus angulosus has been determined. H2B(3) consists of a polypeptide chain of the following 148 amino acid residues: Pro-Arg-Ser-Pro-Ala-Lys-Thr-Ser-Pro-Arg-Lys-Gly-Ser-Pro-Arg-Lys-Gly-Ser-Pro-Arg-Lys-Gly-Ser-Pro-Ser-Arg-Lys-Ala-Ser-Pro-Lys-Arg-Gly-Gly-Lys-Gly-Ala-Lys-Arg-Ala-Gly-Lys-Gly-Gly-Arg-Arg-Arg-Arg-Val-Val-Lys-Arg-Arg-Arg-Arg-Arg-Arg-Glu-Ser-Tyr-Gly-Ile-Tyr-Ile-Tyr-Lys-Val-Leu-Lys-Gln-Val-His-Pro-Asp-Thr-Gly-Ile-Ser-Ser-Arg-Ala-Met-Ser-Val-Met-Asn-Ser-Phe-Val-Asn-Asp-Val-Phe-Glu-Arg-Ile-Ala-Ser-Glu-Ala-Ser-Arg-Leu-Thr-Ser-Ala-Asn-Arg-Arg-Ser-Thr-Val-Ser-Ser-Arg-Glu-Ile-gln-Thr-Ala-Val-Arg-Leu-Leu-Leu-Pro-Gly-Glu-Leu-Ala-Lys-His-Ala-Val-Ser-Glu-Gly-Thr-Lys-Ala-Val-Thr-Lys-Tyr-Thr-Thr-Ser-Arg. H2B(3) Parechinus closely resembles HIB(2) Parechinus but has one additional repeating pentapeptide in the amino-terminal region and a serine replacing glycine at position 98.

Histone H2B variants from the erythrocytes of an amphibian, a reptile and a bird

Histones H2B have been isolated from the terminally differentiated diploid erythrocytes of three different classes, amphibia (Xenopus laevis), reptilia (Crocodilus niloticus) and aves (Gallus domesticus). Partial amino acid sequences revealed three regions of sequence variation, each variant involving a single amino acid substitution.

Abnormal behaviour of proline in the isothiocyanate degradation

It has been observed that proline residues often initiate overlaps during sequenator analysis. The cause has been shown to be an abnormally slow cleavage reaction. The kinetics of the cleavage reaction has been studied and found to obey pseudo-first-order kinetics. There are considerable differences in reaction rates depending on the position of proline in the sequence, as demonstrated for the four prolines in the N-terminal section of the H2B histone from chicken.