THE AMINO ACID COMPOSITION OF SOME PURIFIED PROTEINS

Hydrolysis of the sarcoplasmic, myofibrillar and connective tissue proteins of lean beef by alcalase and its relationship to whole meat hydrolysis

The enzymic hydrolysis and solubilisation of the three meat protein fractions have been investigated in order to elucidate some aspects of the hydrolysis of whole beef protein. Much of the water-soluble sarcoplasmic protein fraction was insolubilised on heating for 25 min at 60°C. While most of this insoluble protein was easily resolubilised enzymically, some of it remained insoluble after 5 hours' hydrolysis. Solubilisation of connective tissue by Alcalase after a 3 h reaction increased markedly from 23% at 55°C to 99% at 60°C. This explains the high optimum temperature for solubilisation of whole beef by Alcalase. A significant portion of myofibrillar tissue remained insoluble after 3 hours' reaction. indicating that the majority of the insoluble solids remaining after whole meat hydrolysis at 60°C derived from myofibrillar tissue. There was good agreement between an experimental reaction progress curve for whole beef hydrolysis and one estimated from progress curves for hydrolysis of the three meat protein fractions.

The specificity for κ-casein as the stabilizer of αs-casein and β-casein. I. Replacement of κ-casein by other proteins

The specificity of the interaction betweenκ-casein,αs-casein andβ-casein which forms the basis of micelle stabilization was studied by investigating the extent to whichκ-casein could be replaced by other proteins. Of those tested, only gelatin replacedκ-casein and even it was only 2·5% (w/v) as effective and required a long pre-incubation period. The micelles formed by each ofκ-casein and gelatin withαs-casein and Ca2+were of a similar size to the casein—Ca complexes which compose natural micelles. Gelatin also formed complexes withαs- and withβ-casein at 30°C in the absence of CaCl2. Evidence was obtained that the interactions between gelatin and the caseins had a much stronger ionic component than had those betweenκ-casein and the other caseins. It was concluded that the interactions betweenκ-casein andαs- andβ-caseins which lead to micelle formation are highly specific and probably involve definite sites in each molecule.

Metabolism in hyperthermophilic microorganisms

Hyperthermophilic microorganisms grow at temperatures of 90 degrees C and above and are a recent discovery in the microbial world. They are considered to be the most ancient of all extant life forms, and have been isolated mainly from near shallow and deep sea hydrothermal vents. All but two of the nearly twenty known genera are classified as Archaea (formerly archaebacteria). Virtually all of them are strict anaerobes. The majority are obligate heterotrophs that utilize proteinaceous materials as carbon and energy sources, although a few species are also saccharolytic. Most also depend on the reduction of elemental sulfur to hydrogen sulfide (H2S) for significant growth. Peptide fermentation involves transaminases and glutamate dehydrogenase, together with several unusual ferredoxin-linked oxidoreductases not found in mesophilic organisms. Similarly, a novel pathway based on a partially non-phosphorylated Entner-Doudoroff scheme has been postulated to convert carbohydrates to acetate, H2 and CO2, although a more conventional Embden-Meyerhof pathway has also been identified in one saccharolytic species. The few hypethermophiles known that can assimilate CO2 do so via a reductive citric acid cycle. Two S(o)-reducing enzymes termed sulfhydrogenase and sulfide dehydrogenase have been purified from the cytoplasm of a hyperthermophile that is able to grow either with or without S(o). A scheme for electron flow during the oxidation of carbohydrates and peptides and the reduction of S(o) has been proposed. However, the mechanisms by which S(o) reduction is coupled to energy conservation in this organism and in obligate S(o)-reducing hyperthermophiles is not known.

Amino Acid Requirements of Two Hyperthermophilic Archaeal Isolates from Deep-Sea Vents, Desulfurococcus Strain SY and Pyrococcus Strain GB-D

Two sulfur-dependent hyperthermophilic archaea, Desulfurococcus strain SY and Pyrococcus strain GB-D, which were isolated from deep-sea hydrothermal vents, utilized free amino acids and peptides obtained from various molecular size fractions of yeast extract. It was found that 11 amino acids were essential for growth. The metabolic products were acetate, i -butyrate, and i -valerate.

The transfer coefficients for L-valine and the rate of incorporation of L-[1-14C] valine into proteins in normal adult rat brain

An autoradiographic method for the measurement of the rate of valine incorporation into brain proteins is described. The transfer coefficients for valine into and out of the brain and the rate of valine incorporation into normal rat brain proteins are given. The valine incorporation and the transfer constants of valine between different biological compartments are provided for 14 gray matter and 2 white matter structures of an adult rat brain. The rate of valine incorporation varies between 0.52 +/- 0.19 nmol/g/min in white matter and 1.94 +/- 0.47 in inferior colliculus (gray matter). Generally, the rate of valine incorporation is about three to four times higher in the gray matter than in the white matter structures.

Isolation and characterization of a cyclic AMP receptor protein from luminous Vibrio harveyi cells

A cAMP receptor protein (CRP) species was purified from the luminous Vibrio harveyi cells to apparent homogeneity. This protein had a dimeric structure with a molecular weight of 23,000 per subunit. Among all eight nucleotides tested, only cAMP (Kd = 3 to 4 microM at 0 degrees C and 52 microM at 23 degrees C) and cGMP (Kd = 6 to 10 microM at 0 degrees C and 67 microM at 23 degrees C) bound to this protein. Its binding to poly(dI-dC), poly(dA-dT), and DNA fragments isolated from V. harveyi cells were all significantly enhanced by the addition of cAMP. Based on patterns of limited proteolysis by trypsin, this CRP assumes different conformations in the absence and presence of cAMP. Also consistent with this conclusion is the finding that the binding of cAMP to CRP induced about 50% quenching of the CRP fluorescence with a concomitant 3-nm blue shift from the original 336-nm emission peak. The binding of cGMP resulted in similar fluorescence changes but had no apparent effect on the pattern of proteolysis by trypsin. Using an in vitro transcription system known to be dependent on cAMP and Escherichia coli CRP, the synthesis of a run-off transcript product was also significantly enhanced by cAMP and this V. harveyi CRP.

The complete amino-acid sequence of hen ovalbumin

The complete amino acid sequence of hen ovalbumin, comprising 385 residues, has been determined. The sequence was deduced from the 17 cyanogen bromide fragments and from peptides derived by digestion with a number of proteolytic enzymes. The molecular weight of the polypeptide chain of ovalbumin is 42699. Ovalbumin has four sites of postsynthetic modification; in addition to the acetylated N terminus, the carbohydrate moiety is located at Asn-292, and the two phosphorylated serines are at residues 68 and 344. The 'signal sequence' of ovalbumin is between residues 234 and 252. The heptapeptide released during the conversion of ovalbumin to plakalbumin by subtilisin digestion corresponds to residues 346-352. The hen ovalbumin polymorphism characterised by an Asn leads to Asp replacement results from a mutation at residue 311. The amino acid sequence of ovalbumin deduced from these amino acid sequence studies is in complete agreement with the sequence of mRNA determined by McReynolds et al. [Nature (Lond.) 273, 723-728 (1978)].

A trypsin and chymotrypsin inhibitor from the metacestodes of Taenia pisiformis

The metacestodes of Taenia pisiformis have been shown to contain a protease inhibitor capable of inactivating the esterolysis of N-alpha-benzoyl-L-arginine ethyl ester (BAEE) and N-benzoyl-L-tyrosine ethyl ester (BTEE) by trypsin and chymotrypsin, respectively, of bovine, dog and rabbit origin, but not affecting the hydrolytic activity of subtilisin, elastase, collagenase, pepsin, rennin and papain. This inhibitor has been demonstrated in whole worm extracts and in the incubation medium of in vitro-maintained, intact living metacestodes. The protease inhibitor which was purified by trichloroacetic acid precipitation, Sephadex G-100 chromatography and affinity chromatography on CNBr-activated Sepharose 4B-bovine, chymotrypsin conjugate was soluble in 5% trichloroacetic acid, withstood heat up to 80 degrees C, tolerated the pH range 1.5 to 9.0, was unaffected by 8 M urea or 0.2 M 2-mercaptoethanol and had a molecular weight of about 7000 to 7200, as calculated from its gel chromatographic behaviour. Complex formation between the inhibitor and the enzymes required 3--4 min for completion. The enzyme-inhibitor complex was not dissociated by 4 M KCl. Activity determinations on bovine TPCK-trypsin and bovine chymotrypsin with BAEE and BTEE assays revealed that the inhibitory actions toward both enzymes are functions of the same or closely adjacent sites of the inhibitor molecule. The supposed function of the inhibitor is discussed.

Structures and apoprotein linkages of phycoerythrobilin and phycocyanobilin

Phycoerythrobilin and phycocyanobilin are covalently attached to the apoproteins of phycoerythrins and phycocyanins. One linkage consists of an ester bond between the hydroxy group of a serine residue and the propionate side chain on one of the inner pyrrole rings (probably ring C). The other linkage is a labile thioether bond between a cysteine residue and the two-carbon side chain on pyrrole ring A. This side chain and both of the alpha-positions of the ring A are in the reduced state. This constitutes an important structural revision, since, in the structures currently accepted for the phycobilins, the two-carbon side chain on ring A is depicted as an ethylidene grouping and this has been regarded not only as a very characteristic feature of the phycobilins, but also as a probable structural feature of the chromophore of phytochrome, largely on the basis of other analogies with the phycobilins. The ethylidene-containing structures apply instead to artefact forms of the pigments released from the apoproteins by treatment with hot methanol. Cleavage of the ring-A linkage involves an elimination reaction releasing the cysteine residue and generating a double bond in the ring-A side chain. During cleavage in methanol the direction of the elimination is towards the ring, generating the ethylidene double bond. Since this is linked to the conjugated system, the methanol-released pigments differ spectrally from the native phycobilins. During acid-catalysed release of the pigments, the elimination apparently goes in the opposite direction, generating a double bond at the outer position of the side chain. Since this double bond is not linked to the conjugated system, the acid-released pigments remain spectrally identical with their protein-bound counterparts.

Isolation and characterization of gas vesicles from Microcyclus aquaticus

Intact gas vesicles of Microcyclus aquaticus S1 were isolated by using centrifugally accelerated flotation of vesicles and molecular sieve chromatography. Isolated gas vesicles were cylindrical organelles with biconical ends and measured 250x100nm. The gas vesicle membrane was composed almost entirely of protein; neither lipid nor carbohydrate was detected, although one mole of phosphate per mole of protein was found. Amino acid analysis indicated that the protein contained 54.6% hydrophobic amino acid residues, lacked sulfur-containing amino acids, and had a low aromatic amino acid content. The protein subunit composition of the vesicles was determined by gel electrophoresis in (i) 0.1% sodium dodecyl sulfate at pH 9.0 and (ii) 5 M urea at pH 2.0. The membrane appeared to consist of one protein subunit of MW 50000 daltons. Charge isomers of this subunit were not detected on urea gels. Antiserum prepared against purified gas vesicles of M. aquaticus S1 crossreacted with the gas vesicles of all other gas vacuolate strains of M. aquaticus, as well as those of Prosthecomicrobium pneumaticum, Nostoc muscorum, and Anabaena flos-aquae, indicating that the gas vesicles of these widely divergent organisms have some antigenic determinants in common.

Quantitative microanalysis of cell walls of Saprolegnia diclina Humphrey and Tremella mesenterica Fries

Cell walls of the fungi Saprolegnia declina Humphrey and Tremella mesenterica Fries were analyzed quantitatively. Particular attention was paid to the hydrolysis and analysis of neutral sugars, amino sugars and amino acids. These components, together with total lipids, total uronic acids and the ashed residue, accounted for more than 90% by weight of the original dry cell wall preparation. There were substantial losses of amino acids during hydrolysis; however, analytical recovery approached 100% when total protein was calculated from the total nitrogen analysis. The analytical procedures were reproducible (+/- 3% for amino acids and amino sugars, and +/- 5-10% for other components) when applied to individual cell wall preparations. However, even under carefully standardized conditions, different cell wall preparations from the same species showed variable composition. Glucose was the predominant neutral sugar in the cell wall polymers of both species. The amino acid compositions were remarkable in that neither species contained detectable levels of cyst(e)ine. Hydroxyproline was detected in both species. The report from Tremella mesenterica is the first for this amino acid from the cell wall of a Basidiomycete.

Translation of ovalbumin mRNA in Xenopus laevis oocytes. Characterization of the system and effects of estrogen on injected mRNA populations

Ovalbumin messenger RNA (mRNAov) purified from hen oviduct was injected into Xenopus laevis oocytes. The oocytes were incubated in culture medium containing [3H]leucine. Analysis of the oocyte cytosol on Sephadex G-15O columns demonstrated a peak of radioactivity which cochromatographed with authentic ovalbumin. Radioactive protein contained in this peak was precipitated by ovalbumin antiserum, coelectrophoresed with ovalbumin on sodium dodecyl sulfate (SDS) and urea gels at pH 8.7, and eluted with the protein at the same pH (4.8) on CM-cellulose chromatography. Injection of increasing amounts of mRNAov was found to elicit a linear response in terms of ovalbumin synthesis. Moreover, there was linear incorporation of radioactivity into microinjected oocytes over a minimum period of 91 h. Less than 1 ng mRNAov was detected in this system. Ovalbumin mRNA activity was present in RNA preparations from chicks treated with estrogen but was undetectable in animals withdrawn from the hormone. This study constitutes an initial demonstration of a steroid hormone-induced alteration in mRNA population as assayed in intact viable heterologous cells.

A new neuraminic acid derivative and three types of glycopeptides isolated from the Cuvierian tubules of the sea cucumber Holothuria forskali

The Cuvierian tubules of Holothuria forskali Della Chiaje, a sea cucumber found in the Adriatic Sea, were investigated with regard to their carbohydrate moieties. From a Pronase digest of these tubules three types of carbohydrate units were isolated and characterized. 1. A high-molecular-weight glycopeptide fraction was shown to contain sulphated polyfucose, galactosamine, a uronic acid and a previously unknown neuraminic acid derivative. The sulphate was shown by i.r. analysis to be present as an O-ester. The carbohydrate unit was linked O-glycosidically to threonine and serine residues in the polypeptide chain. The hitherto unknown neuraminic acid derivative (Hf-neuraminic acid) was resistant to enzymic cleavage by neuraminidase, even after mild alkaline hydrolysis for the removal of O-acyl residues. However, the glycosidic linkage of this compound to the other part of the carbohydrate moiety was readily cleaved by mild acid hydrolysis. Its chromatographic properties distinguished Hf-neuraminic acid from other known neuraminic acid derivatives (N-acetyl-, NO-diacetyl-, NOO-triacetyl- and N-glycollyl-neuraminic acid). Further, this acidic sugar was shown to possess neuraminic acid as its basic structure. Thus, an as yet unknown substituent lends the distinct properties to Hf-neuraminic acid. 2. The carbohydrate composition of a second glycopeptide fraction consisting of a derivative of neuraminic acid, galactose, mannose and glucosamine was similar to that of the well-known carbohydrate groups of the globular glycoproteins. 3. The third fraction contained two glycopeptides containing the disaccharide, glucosylgalactose, which was shown to be linked to the hydroxyl group of hydroxylysine residues of a collagen-like protein. Approximately half of these residues were glycosylated. In addition to these glycopeptides, a small amount of a third glycopeptide that carried only a galactosyl residue was detected. The amino acid sequence of the two major compounds were found to be Gly-Ala-Hyl*-Gly-Ser and Gly-Pro-Hyl*-Gly-Asp, where Hyl* represents a glycosylated amino acid residue.

Amino acid composition of human nasal mucus. Normal subjects

A profile of the proportions of the amino acids of the nasal secretion will enhance our understanding of nasal physiology. For the clinician, today this might be an interesting fact especially because this mucous secretion differs from mucous secretions produced elsewhere. For the future, it might be worked into the practical aspects of clinical practice. For the researcher, it furnishes another step in building the complete picture of nasal physiology. To supply this information nine composites from 55 individual specimens of nasal secretion from normal persons were subjected to acid hydrolysis and quantitative amino acid estimation. Sixteen amino acids were found regularly. Analytical recovery factors were determined for the individual amino acids, and, from these, mole percentages in the original mucus were estimated. The 16 amino acids in order of decreasing abundance were: proline, glutamic acid, glycine, serine, leucine, lysine, alanine, threonine, aspartic acid, valine, arginine, phenlyalanine, tryptophan, tyrosine, isoleucine and histidine. In the nasal mucus, a relatively high proline content is balanced by a relatively lower content of threonine and serine than in other types of mucus. Compared with the proportions of free amino acids in blood plasma, the nasal mucus has a much higher content of the dicarboxylic glutamic and aspartic acids, and a much lower content of alanine and valine.

Comparative electrophoretic and amino acid analyses of isolated membranes from Streptococcus pyogenes and stabilized L-form

Major quantitative, but not qualitative, differences in the various species of proteins in purified membranes from Streptococcus pyogenes and its stabilized L-form have been demonstrated by acidic and alkaline disc gel electrophoresis with and without urea. The fact that no significant differences in the amino acid content or composition between these two membranes could be demonstrated emphasizes that these results are probably due to changes in the relative amounts of the various species of proteins in this subcellular component. The possibility of these protein changes in the L-form membrane being related to its inability to synthesize a rigid cell wall is discussed. Finally, phage-associated lysin, routinely used for removal of the group A streptococcal cell wall, does not appear to affect the protein profile or amino acid composition of the membrane either metabolically or nonmetabolically.

The composition of the cell wall of Fusicoccum amygdali

1. The cell wall of Fusicoccum amygdali consisted of polysaccharides (85%), protein (4-6%), lipid (5%) and phosphorus (0.1%). 2. The main carbohydrate constituent was d-glucose; smaller amounts of d-glucosamine, d-galactose, d-mannose, l-rhamnose, xylose and arabinose were also identified, and 16 common amino acids were detected. 3. Chitin, which accounted for most of the cell-wall glucosamine, was isolated in an undegraded form by an enzymic method. Chitosan was not detected, but traces of glucosamine were found in alkali-soluble and water-soluble fractions. 4. Cell walls were stained dark blue by iodine and were attacked by alpha-amylase, with liberation of glucose, maltose and maltotriose, indicating the existence of chains of alpha-(1-->4)-linked glucopyranose residues. 5. Glucose and gentiobiose were liberated from cell walls by the action of an exo-beta-(1-->3)-glucanase, giving evidence for both beta-(1-->3)- and beta-(1-->6)-glucopyranose linkages. 6. Incubation of cell walls with Helix pomatia digestive enzymes released glucose, N-acetyl-d-glucosamine and a non-diffusible fraction, containing most of the cell-wall galactose, mannose and rhamnose. Part of this fraction was released by incubating cell walls with Pronase; acid hydrolysis yielded galactose 6-phosphate and small amounts of mannose 6-phosphate and glucose 6-phosphate as well as other materials. Extracellular polysaccharides of a similar nature were isolated and may be formed by the action of lytic enzymes on the cell wall. 7. About 30% of the cell wall was resistant to the action of the H. pomatia digestive enzymes; the resistant fraction was shown to be a predominantly alpha-(1-->3)-glucan. 8. Fractionation of the cell-wall complex with 1m-sodium hydroxide gave three principal glucan fractions: fraction BB had [alpha](D) +236 degrees (in 1m-sodium hydroxide) and showed two components on sedimentation analysis; fraction AA(2) had [alpha](D) -71 degrees (in 1m-sodium hydroxide) and contained predominantly beta-linkages; fraction AA(1) had [alpha](D) +40 degrees (in 1m-sodium hydroxide) and may contain both alpha- and beta-linkages.