The amino acid sequence of human chorionic gonadotropin. The alpha subunit and beta subunit.

The amino acid sequences of both the alpha and beta subunits of human chorionic gonadotropin have been determined. The amino acid sequence of the alpha subunit is: Ala - Asp - Val - Gln - Asp - Cys - Pro - Glu - Cys-10 - Thr - Leu - Gln - Asp - Pro - Phe - Ser - Gln-20 - Pro - Gly - Ala - Pro - Ile - Leu - Gln - Cys - Met - Gly-30 - Cys - Cys - Phe - Ser - Arg - Ala - Tyr - Pro - Thr - Pro-40 - Leu - Arg - Ser - Lys - Lys - Thr - Met - Leu - Val - Gln-50 - Lys - Asn - Val - Thr - Ser - Glu - Ser - Thr - Cys - Cys-60 - Val - Ala - Lys - Ser - Thr - Asn - Arg - Val - Thr - Val-70 - Met - Gly - Gly - Phe - Lys - Val - Glu - Asn - His - Thr-80 - Ala - Cys - His - Cys - Ser - Thr - Cys - Tyr - Tyr - His-90 - Lys - Ser. Oligosaccharide side chains are attached at residues 52 and 78. In the preparations studied approximately 10 and 30% of the chains lack the initial 2 and 3 NH2-terminal residues, respectively. This sequence is almost identical with that of human luteinizing hormone (Sairam, M. R., Papkoff, H., and Li, C. H. (1972) Biochem. Biophys. Res. Commun. 48, 530-537). The amino acid sequence of the beta subunit is: Ser - Lys - Glu - Pro - Leu - Arg - Pro - Arg - Cys - Arg-10 - Pro - Ile - Asn - Ala - Thr - Leu - Ala - Val - Glu - Lys-20 - Glu - Gly - Cys - Pro - Val - Cys - Ile - Thr - Val - Asn-30 - Thr - Thr - Ile - Cys - Ala - Gly - Tyr - Cys - Pro - Thr-40 - Met - Thr - Arg - Val - Leu - Gln - Gly - Val - Leu - Pro-50 - Ala - Leu - Pro - Gin - Val - Val - Cys - Asn - Tyr - Arg-60 - Asp - Val - Arg - Phe - Glu - Ser - Ile - Arg - Leu - Pro-70 - Gly - Cys - Pro - Arg - Gly - Val - Asn - Pro - Val - Val-80 - Ser - Tyr - Ala - Val - Ala - Leu - Ser - Cys - Gln - Cys-90 - Ala - Leu - Cys - Arg - Arg - Ser - Thr - Thr - Asp - Cys-100 - Gly - Gly - Pro - Lys - Asp - His - Pro - Leu - Thr - Cys-110 - Asp - Asp - Pro - Arg - Phe - Gln - Asp - Ser - Ser - Ser - Ser - Lys - Ala - Pro - Pro - Pro - Ser - Leu - Pro - Ser-130 - Pro - Ser - Arg - Leu - Pro - Gly - Pro - Ser - Asp - Thr-140 - Pro - Ile - Leu - Pro - Gln. Oligosaccharide side chains are found at residues 13, 30, 121, 127, 132, and 138. The proteolytic enzyme, thrombin, which appears to cleave a limited number of arginyl bonds, proved helpful in the determination of the beta sequence.     

NH2-terminal sequences of DNA-, heparin-, and gelatin-binding tryptic fragments from human plasma fibronectin

NH₂-terminal sequence analysis was performed on subregions of human plasma fibronectin including 24,000-dalton (24K) DNA-binding, 29,000-dalton (29K) gelatin-binding, and 18,000-dalton (18K) heparin-binding tryptic fragments. These fragments were obtained from fibronectin after extensive trypsin digestion followed by sequential affinity purification on gelatin-Sepharose, heparin-agarose, and DNA-cellulose columns. The gelatin-binding fragment was further purified by gel filtration on Sephadex G-100, and the DNA-binding and heparin-binding fragments were further purified by high-performance liquid chromatography. The 29K fragment had the following NH₂-terminal sequence: AlaAlaValTyrGlnProGlnProHisProGlnProPro (Pro)TyrGlyHis HisValThrAsp(His)(Thr)ValValTyrGly(Ser) ?(Ser)?-Lys. The NH₂-terminal sequence of a 50K, gelatin-binding, subtilisin fragment by L. I. Gold, A. Garcia-Pardo, B. Prangione, E. C. Franklin, and E. Pearlstein (1979, Proc. Nat. Acad. Sci. USA76, 4803–4807) is identical to positions 3–19 (with the exception of some ambiguity at position 14) of the 29K fragment. These data strongly suggest that the 29K tryptic fragment is included in the 50K subtilisin fragment, and that subtilisin cleaves fibronectin between the Ala²Val³ residues of the 29K tryptic fragment. The 18K heparin-binding fragment had the following NH₂-terminal sequence: (Glu)AlaProGlnProHisCysIleSerLysTyrIle LeuTyrTrpAspProLysAsnSerValGly?(Pro) LysGluAla?(Val)(Pro). The 29K gelatin-binding and 18K heparin-binding fragments have proline-rich NH₂-terminal sequences suggesting that they may have arisen from protease-sensitive, random coil regions of fibronectin corresponding to interdomain regions preceding macromolecular-binding domains. Both of these fragments contain the identical sequence ProGlnProHis, a sequence which may be repeated in other interdomain regions of fibronectin. The 24K DNA-binding fragment has the following NH₂-terminal sequence: SerAspThrValProSerProCysAspLeuGlnPhe ValGluValThrAspVal LysValThrIleMetTrpThrProProGluSerAla ValThrGlyTyrArgVal AspValCysProValAsnLeuProGlyGluHisGly Gln(Cys)LeuProIleSer. The sequence of positions 9–22 are homologous to positions 15–28 of the α chain of DNA-dependent RNA polymerase from Escherichia coli. The homology observed suggests that this stretch of amino acids may be a DNA-binding site.     

Solution structure of marinostatin, a natural ester-linked protein protease inhibitor

Marinostatin is a unique protein protease inhibitor containing two ester linkages. We have purified a 12-residue marinostatin [MST(1-12), (1)FATMRYPSDSDE(12)] and determined the residues involved in the formation of the ester linkages and the solution structure by (1)H NMR spectroscopy and restrained molecular dynamics calculation. The two ester linkages of MST(1-12) are formed between hydroxyl and carboxyl groups, Thr(3)-Asp(9) and Ser(8)-Asp(11), indicating that MST(1-12) has two cyclic regions which are fused at the residues of Ser(8) and Asp(9). A strong NOE cross-peak between Tyr(6) H(alpha) and Pro(7) H(alpha) was observed, indicating that the Pro(7) residue takes a cis-conformation. Well-converged structures and hydrogen-deuterium experiments of MST(1-12) showed that the backbone NH proton of the P1'residue, Arg(5), is hydrogen-bonded to the carbonyl oxygen of the ester linkage between Thr(3) and Asp(9). To reveal the significance of the ester linkages, a marinostatin analogue, MST-2SS ((1)FACMRYPCCSCE(12)) with two disulfide bridges of Cys(3)-Cys(9) and Cys(8)-Cys(11), was also synthesized. The inhibitory activity of MST-2SS was as strong as that of MST(1-12), and the Pro(7) residue of MST-2SS also takes a cis-conformation. However, the exchange rate of the Arg(5) NH proton of MST-2SS was about 100 times faster than that of MST(1-12), and the structure calculation of MST-2SS was not converged on account of the small number of NOEs, indicating that MST-2SS takes a more flexible structure. The hydrogen acceptability of the ester linkage formed by the P2 position residue, Thr(3), is crucial for suppressing the fluctuation of the reactive site and sustaining the inhibitory activity, which enables marinostatin to be one of the smallest protease inhibitors in nature.     

Express analysis of protein amino acid sequences. Primary structure of Penicillium chrysogenum 152A guanyl-specific ribonuclease

The complete amino acid sequence of Penicillium chrysogenum 152A guanyl-specific RNase has been established using automated Edman degradation of two non-fractionated peptide mixtures produced by tryptic and staphylococcal protease digests of the protein. The RNase contains 102 amino acid residues: His2, Arg3, Asp7, Asn8, Thr5, Ser11, Glu4, Gln2, Pro4, Gly11, Ala13, Cys4, Val8, Ile3, Leu3, Tyr9, Phe5 (Mr 10 747).     

Multiple binding modes for palmitate to barley lipid transfer protein facilitated by the presence of proline 12

Molecular dynamics simulations have been used to characterise the binding of the fatty acid ligand palmitate in the barley lipid transfer protein 1 (LTP) internal cavity. Two different palmitate binding modes (1 and 2), with similar protein–ligand interaction energies, have been identified using a variety of simulation strategies. These strategies include applying experimental protein–ligand atom–atom distance restraints during the simulation, or protonating the palmitate ligand, or using the vacuum GROMOS 54B7 force‐field parameter set for the ligand during the initial stages of the simulations. In both the binding modes identified the palmitate carboxylate head group hydrogen bonds with main chain amide groups in helix A, residues 4 to 19, of the protein. In binding mode 1 the hydrogen bonds are to Lys 11, Cys 13, and Leu 14 and in binding mode 2 to Thr 15, Tyr 16, Val 17, Ser 24 and also to the OH of Thr 15. In both cases palmitate binding exploits irregularity of the intrahelical hydrogen‐bonding pattern in helix A of barley LTP due to the presence of Pro 12. Simulations of two variants of barley LTP, namely the single mutant Pro12Val and the double mutant Pro12Val Pro70Val, show that Pro 12 is required for persistent palmitate binding in the LTP cavity. Overall, the work identifies key MD simulation approaches for characterizing the details of protein–ligand interactions in complexes where NMR data provide insufficient restraints.     

Enzymatic inactivation of bradykinin by rat brain neuronal perikarya

1. Bradykinin (Bk; Arg1-Pro2-Pro3-Gly4-Phe5-Ser6-Pro7-Phe8-Arg8) inactivation by bulk isolated neurons from rat brain is described. 2. Bk is rapidly inactivated by neuronal perikarya (4.2 +/- 0.6 fmol/min/cell body). 3. Sites of inactivating cleavages, determined by a kininase bioassay combined with a time-course Bk-product analysis, were the Phe5-Ser6, Pro7-Phe8, Gly4-Phe5, and Pro3-Gly4 peptide bonds. The cleavage of the Phe5-Ser6 bond inactivated Bk at least five fold faster than the other observed cleavages. 4. Inactivating peptidases were identified by the effect of inhibitors on Bk-product formation. The Phe5-Ser6 bond cleavage is attributed mainly to a calcium-activated thiol-endopeptidase, a predominantly soluble enzyme which did not behave as a metalloenzyme upon dialysis and was strongly inhibited by N-[1(R,S)-carboxy-2-phenylethyl]-Ala-Ala-Phe-p-aminobenzoate and endo-oligopeptidase A antiserum. Thus, neuronal perikarya thiol-endopeptidase seems to differ from endo-oligopeptidase A and endopeptidase 24.15. 5. Endopeptidase 24.11 cleaves Bk at the Gly4-Phe5 and, to a larger extent, at the Pro7-Phe8 bond. The latter bond is also cleaved by angiotensin-converting enzyme (ACE) and prolyl endopeptidase (PE). PE also hydrolyzes Bk at the Pro3-Gly4 bond. 6. Secondary processing of Bk inactivation products occurs by (1) a rapid cleavage of Ser6-Pro7-Phe8-Arg8 at the Pro7-Phe8 bond by endopeptidase 24.11, 3820ACE, and PE; (2) a bestatin-sensitive breakdown of Phe8-Arg9; and (3) conversion of Arg1-Pro7 to Arg1-Phe5, of Gly4-Arg9 to both Gly4-Pro7 and Ser6-Arg9, and of Phe5-Arg9 to Ser6-Arg9, Phe8-Arg9, and Ser6-Pro7, by unidentified peptidases. 7. A model for the enzymatic inactivation of bradykinin by rat brain neuronal perikarya is proposed.     

Synthetic peptide derived from alpha-fetoprotein inhibits growth of human breast cancer: investigation of the pharmacophore and synthesis optimization.

Asynthetic peptide that inhibits the growth of estrogen receptor positive (ER+) human breast cancers, growing as xenografts in mice, has been reported. The cyclic 9-mer peptide, cyclo[EMTOVNOGQ], is derived from alpha-fetoprotein (AFP), a safe, naturally occurring human protein produced during pregnancy, which itself has anti-estrogenic and anti-breast cancer activity. To determine the pharmacophore of the peptide, a series of analogs was prepared using solid-phase peptide synthesis. Analogs were screened in a 1-day bioassay, which assessed their ability to inhibit the estrogen-stimulated growth of uterus in immature mice. Deletion of glutamic acid, Glu1, abolished activity of the peptide, but glutamine (Gln) or asparagine (Asn) could be substituted for Glu1 without loss of activity. Methionine (Met2) was replaced with lysine (Lys) or tyrosine (Tyr) with retention of activity. Substitution of Lys for Met2 in the cyclic molecule resulted in a compound with activity comparable with the Met2-containing cyclic molecule, but with a greater than twofold increase in purity and corresponding increase in yield. This Lys analog demonstrated anti-breast cancer activity equivalent to that of the original Met-containing peptide. Therefore, Met2 is not essential for biologic activity and substitution of Lys is synthetically advantageous. Threonine (Thr3) is a nonessential site, and can be substituted with serine (Ser), valine (Val), or alanine (Ala) without significant loss of activity. Hydroxyproline (Hyp), substituted in place of the naturally occurring prolines (Pro4, Pro7), allowed retention of activity and increased stability of the peptide during storage. Replacement of the first Pro (Pro4) with Ser maintains the activity of the peptide, but substitution of Ser for the second Pro (Pro7) abolishes the activity of the peptide. This suggests that the imino acid at residue 7 is important for conformation of the peptide, and the backbone atoms are part of the pharmacophore, but Pro4 is not essential. Valine (Val5) can be substituted only with branched-chain amino acids (isoleucine, leucine or Thr); replacement by d-valine or Ala resulted in loss of biologic activity. Thus, for this site, the bulky branched side chain is essential. Asparagine (Asn6) is essential for activity. Substitution with Gln or aspartic acid (Asp), resulted in reduction of biologic activity. Removal of glycine (Gly8) resulted in a loss of activity but nonconservative substitutions can be made at this site without a loss of activity indicating that it is not part of the pharmacophore. Cyclization of the peptide is facilitated by addition of Gln9, but this residue does not occur in AFP nor is it necessary for activity. Gln9 can be replaced with Asn, resulting in a molecule with similar activity. These data indicate that the pharmacophore of the peptide includes side chains of Val5 and Asn6 and backbone atoms contributed by Thr3, Val5, Asn6, Hyp7 and Gly8. Met2 and Gln9 can be modified or replaced. Glu1 can be replaced with charged amino acids, and is not likely to be part of the binding site of the peptide. The results of this study provide information that will be helpful in the rational modification of cyclo[EMTOVNOGQ] to yield peptide analogs and peptidomimetics with advantages in synthesis, pharmacologic properties, and biologic activity.     

Identification of coding polymorphisms in human circadian rhythm genes PER1, PER2, PER3, CLOCK, ARNTL, CRY1, CRY2 and TIMELESS in a multi-ethnic screening panel.

STUDY OBJECTIVE: In this study, the exonic regions of the circadian rhythm genes PER1, PER2, PER3, CLOCK, ARNTL, CRY1, CRY2 and TIMELESS were re-sequenced and coding changes identified in a panel of 95 individuals varying in ethnicity. STUDY PARTICIPANTS: DNA screening panel consisting of 95 DNA samples (17 American Caucasians, 17 African Americans, 8 Ashkenazi Jews, 8 Chinese, 8 Japanese, 5 Mexican Indians, 8 Mexicans, 8 Northern Europeans, 8 Puerto Ricans, and 8 South Americans) selected from the Coriell Institute Human Variation Panel. RESULTS: In addition to coding changes already identified in the database dbSNP, novel coding changes were identified, including PER1: Pro37Ser, Pro351Ser, Gln988Pro, Ala998Thr; PER2: Leu83Arg, Leu157Leu, Thre174Ile, Phe400Phe, Pro822Pro, Ala828Thr, Ala861Val, Phe876Leu, Val883Met, Val903Ile, Ala923Pro; PER3: Pro67Pro, Val90Ile, His638His, Ala820Ala, Leu929Leu; ARNTL: Arg166Gln, Ser459Phe; CLOCK: Ala34Ala, Ser208Cys, Phe233Phe, Ser632Thr, Ser816Ser; TIMELESS: Met870Val and CRY2: His35His. No coding polymorphisms were identified in CRY1. CONCLUSIONS: Considerable genetic variation occurs within the coding region of the genes regulating circadian rhythm. Many of the non-synonymous coding polymorphisms could affect protein structure/function with the potential to affect molecular regulation of the sleep/wake cycle. Many of the potential functional effects could be ethnic group specific.     

Polyproline, beta-turn helices. Novel secondary structures proposed for the tandem repeats within rhodopsin, synaptophysin, synexin, gliadin, RNA polymerase II, hordein, and gluten

Seven proteins each contain 8 to 52 tandem repeats of a unique class of oligopeptide. The consensus peptide for each is rhodopsin Tyr Pro Pro Gln Gly synaptophysin Tyr Gly Pro Gln Gly synexin Tyr Pro Pro Pro Pro Gly gliadin Tyr Pro Pro Pro Gln Pro RNA polymerase II Tyr Ser Pro Thr Ser Pro Ser hordein Phe Pro Gln Gln Pro Gln Gln Pro gluten Tyr Pro Thr Ser Pro Gln Gln Gly Tyr Although there is obvious variation of sequence and of length, the penta- to nonapeptides share an initial Tyr (or Phe) and have high Pro contents and abundant Gly, Gln, and Ser. We have evaluated helical models that both recognize the uniqueness of these sequence repeats and accommodate variations on the basic theme. We have developed a group of related helical models for these proteins with about three oligopeptide repeats per turn of 10-20 A. These models share several common features: Most of the phi dihedral angles are -54 degrees, to accommodate Pro at all positions except the first (Tyr). Except for the beta-turns, most psi dihedral angles are near +140 degrees as found in polyproline. Each oligopeptide has at least one beta-turn; several have two. Some contain a cis-Tyr, Pro peptide bond; a few have a cis-bond plus one beta-turn. Tyr side chains vary from totally exposed to buried within the helices and could move to accommodate either external hydrophobic interactions or phosphorylation. The several related structures seem to be readily interconverted without major change in the overall helical parameters, and therein may lie the key to their functions.     

Schizosaccharomyces pombe carboxyl-terminal domain (CTD) phosphatase Fcp1: distributive mechanism, minimal CTD substrate, and active site mapping

Schizosaccharomyces pombe Fcp1 is an essential protein serine phosphatase that preferentially dephosphorylates Ser(2) of the RNA polymerase II C-terminal domain (CTD) heptad repeat Y(1)S(2)P(3)T(4)S(5)P(6)S(7). Here we show that: (i) Fcp1 acts distributively during the hydrolysis of substrates containing tandem Ser(2)-PO(4) heptads; (ii) the minimal optimal CTD substrate for Fcp1 is a single heptad of phasing S(5)P(6)S(7)Y(1)S(2)P(3)T(4); and (iii) single alanine mutations of flanking residues Tyr(1) or Pro(3) result in 6-fold decrements in CTD phosphatase activity. Fcp1 belongs to the DXDX(T/V) family of phosphotransferases that act via an acyl-phosphoenzyme intermediate. An alanine scan of 11 conserved positions of S. pombe Fcp1 identifies Thr(174), Tyr(237), Thr(243), and Tyr(249) as important for phosphatase activity. Structure-activity relationships at these positions were determined by introducing conservative substitutions. Our results, together with previous mutational studies, highlight a constellation of 11 amino acids that are conserved in all Fcp1 orthologs and likely comprise the active site.     

The primary structure of the β-subunit of protocatechuate 3,4-dioxygenase from Pseudomonas aeruginosa

The complete amino acid sequence of the β-subunit of protocatechuate 3,4-dioxygenase was determined. The β-subunit contained four methionine residues. Thus, five peptides were obtained after cleavage of the carboxymethylated β-subunit with cyanogen bromide, and were isolated on Sephadex G-75 column chromatography. The amino acid sequences of the cyanogen bromide peptides were established by characterization of the peptides obtained after digestion with trypsin, chymotrypsin, thermolysin, or Staphylococcus aureus protease. The major sequencing techniques used were automated and manual Edman degradations. The five cyanogen bromide peptides were aligned by means of the amino acid sequences of the peptides containing methionine purified from the tryptic hydrolysate of the carboxymethylated β-subunit. The amino acid sequence of all the 238 residues was as follows: ProAlaGlnAspAsnSerArgPheValIleArgAsp ArgAsnTrpHis ProLysAlaLeuThrPro-Asp — TyrLysThrSerIleAlaArg SerProArgGlnAla LeuValSerIleProGlnSer — IleSerGluThrThrGly ProAsnPheSerHisLeu GlyPheGlyAlaHisAsp-His — AspLeuLeuLeuAsnPheAsn AsnGlyGlyLeu ProIleGlyGluArgIle-Ile — ValAlaGlyArgValValAsp GlnTyrGlyLysPro ValProAsnThrLeuValGluMet — TrpGlnAlaAsnAla GlyGlyArgTyrArg HisLysAsnAspArgTyrLeuAlaPro — LeuAspProAsn PheGlyGlyValGly ArgCysLeuThrAspSerAspGlyTyrTyr — SerPheArg ThrIleLysProGlyPro TyrProTrpArgAsnGlyProAsnAsp — TrpArgProAla HisIleHisPheGlyIle SerGlyProSerIleAlaThr-Lys — LeuIleThrGlnLeuTyr PheGluGlyAspPro LeuIleProMetCysProIleVal — LysSerIleAlaAsn ProGluAlaValGlnGln LeuIleAlaLysLeuAspMetAsnAsn — AlaAsnProMet AsnCysLeuAlaTyr ArgPheAspIleValLeuArgGlyGlnArgLysThrHis PheGluAsnCys. The sequence published earlier in summary form (Iwaki et al., 1979, J. Biochem.86, 1159–1162) contained a few errors which are pointed out in this paper.     

High-performance liquid chromatography and sensitive detection of amino acids derivatized with 7-fluoro-4-nitrobenzo-2-oxa-1,3-diazole

7-Fluoro-4-nitrobenzo-2-oxa-1,3-diazole is used as a precolumn fluorescent labeling reagent for high-performance liquid chromatography of amino acids, including proline and hydroxyproline. The reaction is run at pH 8.0 at 60°C for 5 min. The fluorophors (Asp, Glu, Hyp, Ser, Gly, Thr, Ala, Pro) are separated on a reversed-phase column (μBondapak C₁₈) with 0.1 m phosphate buffer (pH 6.0) containing 6.75% methanol and 1.8% tetrahydrofuran, and are detected at the level of 10 fmol with excitation at 470 nm and emission at 530 nm.     

Structural basis for executioner caspase recognition of P5 position in substrates

Caspase-3, -6 and -7 cleave many proteins at specific sites to induce apoptosis. Their recognition of the P5 position in substrates has been investigated by kinetics, modeling and crystallography. Caspase-3 and -6 recognize P5 in pentapeptides as shown by enzyme activity data and interactions observed in the crystal structure of caspase-3/LDESD and in a model for caspase-6. In caspase-3 the P5 main-chain was anchored by interactions with Ser209 in loop-3 and the P5 Leu side-chain interacted with Phe250 and Phe252 in loop-4 consistent with 50% increased hydrolysis of LDEVD relative to DEVD. Caspase-6 formed similar interactions and showed a preference for polar P5 in QDEVD likely due to interactions with polar Lys265 and hydrophobic Phe263 in loop-4. Caspase-7 exhibited no preference for P5 residue in agreement with the absence of P5 interactions in the caspase-7/LDESD crystal structure. Initiator caspase-8, with Pro in the P5-anchoring position and no loop-4, had only 20% activity on tested pentapeptides relative to DEVD. Therefore, caspases-3 and -6 bind P5 using critical loop-3 anchoring Ser/Thr and loop-4 side-chain interactions, while caspase-7 and -8 lack P5-binding residues.     

Ferredoxin from a red alga, Porphyra umbilicalis.

A plant-algal type ferredoxin was isolated from the red alga, Porphyra umbilicalis. In its oxidised form the ferredoxin had absorption maxima at 277, (281), 323, 420 and 462 nm. Two atoms each of non-haem iron and labile sulphur were present per molecule protein. The midpoint potential of the protein was -400 mV and it effectively mediated electron transport in the NADP-photoreduction system of barley. The amino acid composition of Porphyra umbilicalis ferredoxin was determined as (Lys4, His2, Arg1, Asx10, Thr8, Ser7, Glx16-17, Pro3, Gly7, Ala8, Cys5, Val6, Met1, Ile5, Leu8, Tyr5, Phe2). The minimum molecular weight of approximately 11000 was confirmed by sedimentation-equilibrium studies in the analytical ultracentrifuge. Approaching half of the total amino acid sequence was determined by means of an automatic sequencer.     

Comparative micelle structure. IV. The similarity between caprine alphas-casein and bovine alphas-3- casein.

The major component of caprine (goat) alphas-casein has been isolated by DEAE-and CM-cellulose chromatography in buffers containing urea and 2-mercaptoethanol. The protein has a molecular weight of 25700 as determined by gel filtration on Sepharose 6B in guanidine hydrochloride. Its composition, Asp17, Thr14, Ser14, Glu45, Pro18, Gly4, Ala10, Cys2, Val12, Met4, Ile12, Leu12, Tyr11, Phe8, His5, Lys22, Arg6, Trp2 and 7 phosphate residues, is much closer to that of bovine alphas3-casein than to bovine alphas1-casein. The caprin alphas-casein is more easily precipitated with Ca2+ than bovine alphas3-casein at 37 degrees C, pH 6.8, which in turn is more easily precipitated than bovine alphas1-casein.