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PubMed1969

Subunit structure of oyster paramyosin.

Paramyosin from the oyster Crassostrea commercialis was studied by equilibrium sedimentation. In non-denaturing solvents the minimum molecular weight is 208000. Dissociation into subunits requires complete disruption of the alpha-helix. This occurs at pH7 in guanidine hydrochloride solutions of concentration greater than 7m in the presence of a disulphide-bond-reducing agent. Solutions of the protein in concentrated guanidine hydrochloride are polydisperse and contain species of low molecular weight (approx. 25000) comprising approx. 5% to 10% of the protein. The molecular weight of the main component is estimated to be 97000 and the paramyosin molecule contains two of these subunits. From the present observations no decision can be made as to whether or not the small component (or components) represents part of the paramyosin molecule. Preferential binding of guanidine hydrochloride to the extent of 0.13g./g. of protein was shown in solutions of paramyosin in 7.85m-guanidine hydrochloride.

Animals↗
PubMed1969

The configuration of 2,6-diamino-3-hydroxypimelic acid in microbial cell walls.

beta-Hydroxydiaminopimelic acid, together with some diaminopimelic acid, occurs in the cell-wall mucopeptide of certain Actinomycetales. These components were converted into their di-DNP derivatives and separated by chromatography. Hence the relative proportions present in the cell walls of a number of species were measured. The problem of acid-induced inversion of configuration was studied. Of the diaminohydroxypimelic acids isomer B (see Scheme 2; amino groups meso, hydroxy group threo to its neighbouring amino group) always predominated but a small proportion of isomer D (amino groups l, hydroxy group erythro) also occurred. The configuration of the diaminohydroxypimelic acids was determined by periodate oxidation to glutamic gamma-semialdehyde, which underwent spontaneous ring-closure. Reduction with sodium borohydride produced optically active proline, the configuration of which was determined by direct measurement of the optical rotation of DNP-proline. Un-cross-linked diaminohydroxypimelic acid in the cell wall was oxidized with periodate in the presence of ammonia. Since the remaining amino group was bound in peptide linkage, ring-closure was prevented and borohydride reduction of the aldehyde-ammonia presumed to be present resulted in the formation of ornithine. The quantity of ornithine was used as a measure of the degree of cross-linking.

Actinomycetales↗
PubMed1970

Products of aminolysis and enzymic hydrolysis of the cephalosporins.

1. The reaction of cephalosporins with ammonia, amino acids and other simple amino compounds in weakly alkaline aqueous solutions yields labile compounds with lambda(max.) 230nm. The reaction of deacetyl- and deacetoxy-cephalosporins under similar conditions yields compounds with lambda(max.) 260nm. 2. Hydrolysis with a beta-lactamase results in the formation of compounds with lambda(max.) 230nm from deacetylcephalosporins and cephalosporins, but not from deacetoxycephalosporins. 3. These different compounds decompose to give penaldates and penamaldates derived from the side chain and the carbon atoms of the beta-lactam ring. 4. Derivatives similar to those obtained with simple amino compounds appear to be formed when cephalosporins and their analogues react with lysine polymers. 5. Some of the chemical and physical properties of the various derivatives have been studied and tentative structures for them are proposed. 6. Possible implications of the results in relation to the immunological properties of the cephalosporins are discussed.

Amino Acids↗
PubMed1970

Physical properties of ribosomal ribonucleic acid isolated from bacteria deficient in ribonuclease I.

1. Bacteria deficient in ribonuclease I were used as a source of stable ribosomal RNA. RNA was isolated from a ribosome fraction of Pseudomonas fluorescens N.C.I.B. 8248 and acetone-treated cells of Escherichia coli M.R.E. 600 by the method developed by Robinson & Wade (1968). 2. The s(20,w) of the 16S and 23S components can vary from 21S and 28S down to 4S depending on the RNA macro-ion concentration and the extent to which charge is suppressed by univalent Na(+) and tris(+) counter-ions or neutralized through the binding of bivalent Mg(2+) to phosphate groups. 3. The primary charge effect in sedimentation and the frictional coefficient (which increases as the molecular conformation expands) both increase with charge and cause a decrease in s value. 4. RNA solutions heated to 80 degrees C for 10min show minor changes in s value and a detectable increase in polydispersity. Millimolar concentrations of Mg(2+) promote heat-instability and so does treatment of RNA solutions with the nuclease adsorbent macaloid, which was found to contaminate the solutions with Mg(2+). 5. The stabilization of secondary structure by univalent and bivalent cations was investigated by optical methods. 6. The sedimentation properties of 30S and 50S ribosomal subunits and their constituent 16S and 23S RNA components were compared and discussed from the viewpoint of unfolding.

Binding Sites↗
PubMed1971

Proteins of normal hair and of cystine-deficient hair from mentally retarded siblings.

1. S-Carboxymethylkerateines extracted from normal hair can be fractionated into high-sulphur and low-sulphur proteins similar to those obtained from sheep's wool. Normal human hair gives a major high-sulphur protein of higher molecular weight and S-carboxymethylcysteine content than any isolated from normal sheep's wool. 2. The proteins from cystine-deficient hair can also be divided into high-sulphur and low-sulphur proteins. There is a lower proportion of high-sulphur protein in cystine-deficient hair than in normal hair. 3. The high-sulphur proteins from cystine-deficient hair have an abnormal amino acid composition and in particular are lower in S-carboxymethylcysteine content than the corresponding proteins from normal hair. New components are present and the content of very high-sulphur proteins of high molecular weight is much decreased. The low-sulphur proteins of cystine-deficient hair are probably also deficient in S-carboxymethylcysteine. 4. The proteins of cystine-deficient hair probably resemble those in the normal hair root, except that disulphide-bridge formation has occurred.

Acrylates↗
PubMed1971

Studies on protein multimers. The association-dissociation behaviour of -galactosidase in glycerol.

1. The effect of glycerol on the association-dissociation behaviour of beta-galactosidases from Escherichia coli is described. Two strains, K12 and ML308, were used as sources of enzyme. The conditions used, involving glycerol at a concentration of 90%, result in dissociation of the active 540000-dalton form to inactive structural subunits of 135000 daltons. 2. A pH-dependent process, assumed to be cyclic in mechanism, allows reassociation to an active form indistinguishable from the initial protein. 3. The apparently identical structural subunits, if produced in the presence of EDTA, were found to give rise to two electrophoretically distinguishable species. 4. Enzymes from both strains of E. coli can be distinguished electrophoretically but exhibit the same behaviour in glycerol. 5. A scheme of the association-dissociation is presented that is consistent with the behaviour observed and that has some predictive value.

Edetic Acid↗
PubMed1972

Thio reduction of human 2 -macroglobulin. The subunit structure.

1. Human alpha(2)-macroglobulin was prepared from a fraction obtained during the large-scale separation of normal human plasma proteins for clinical use. 2. Sedimentation-equilibrium measurements indicated a molecular weight of 725000. A value of 18.1S was obtained for s(0) (20,w). 3. The dissociation that occurs in the pH range 4.5-2.5 and in the region of neutrality in urea-containing solutions is consistent with a dimeric structure of the molecule. 4. The effects of the thiol reagents mercaptoethanol, mercaptoethylamine and N-acetylcysteine were investigated over a range of experimental conditions. Distinct components having sedimentation coefficients of 15, 12 and 8.5S were identified. 5. Conditions were found under which limited reduction with thiol liberated a subunit with a molecular weight approximately one-quarter of that of the intact molecule. This subunit retains the serological specificity of the whole molecule.

Acetylcysteine↗
PubMed1973

A comparaive study of the effects of chemical modification on the immunochemical and optical properties of human plasma low-density lipoprotein(s) and apoproteins.

1. The structure of human plasma low-density lipoprotein(s) [LD lipoprotein(s)] was investigated by several immunological and optical techniques. The effects of delipidation and of chemical modification by 3-carboxypropionylation, acetylation, diazotization and amidination were examined. A sensitive double-antibody radioimmunoassay for human LD lipoproteins is presented and is used to assess the extent of immunochemical modification. A computer best-fit analysis is used to analyse circular-dichorism (c.d.) spectra. These methods permit comparisons of the relative effects of chemical modification and delipidation of LD lipoprotein under similar experimental conditions. 2. 3-Carboxypropionylation, acetylation or diazotization produces qualitative and quantitative changes in the immunochemical properties of LD lipoprotein. Amidination causes minor changes detected by radioimmunoassay but not by double-diffusion experiments. In general, the order of effectiveness in displacing (125)I-labelled LD lipoprotein is amidinated>diazo or acetyl>3-carboxypropionyl derivatives. 3. The order of the extent of conformational alteration induced in apoLD lipoprotein and LD lipoprotein, as judged by c.d. analyses, was 3-carboxypropionylation>diazotization>acetylation or amidination. 4. Delipidation of LD lipoprotein results in immunological alterations that are qualitatively detected by antisera to LD lipoprotein. Four of five antisera to apoLD lipoprotein form precipitin lines of identity between native LD lipoprotein and apoLD lipoprotein in double-diffusion experiments. An anti-(apoLD lipoprotein) serum that forms precipitin lines of complete identity between LD lipoprotein and apoLD lipoprotein reacts differently with these two antigens in radioimmunoassay. ApoLD lipoprotein is only one-fourth to one-half as effective as LD lipoprotein, on a protein basis, in the displacement of (125)I-labelled LD lipoprotein from this anti-(apoLD lipoprotein). 5. Conformational analysis indicates that apoLD lipoprotein retains a high proportion of the structural integrity of the native lipoprotein. Delipidation induces a small decrease in the content of beta-structure and a small increase in disordered structure, without greatly affecting the alpha-helical content. Chemical modification produces more severe conformational changes of apoLD lipoprotein than of LD lipoprotein. Computer analysis of the c.d. spectra of apoLD lipoprotein indicates that addition of high concentrations of sodium decyl sulphate abolishes most of the beta-conformation concomitant with increases in alpha-helical and disordered structure. 6. There is parallelism between the alteration of the charge of LD lipoprotein and apoLD lipoprotein and the extent of immunochemical and conformational changes.

Acylation↗
PubMed1975

The extraction and characterization of bovine epidermal alpha-keratin.

1. The alpha-fibrous protein (alpha-keratin) component of bovine epidermis has been extracted and characterized. 2. Prekeratin, a multichain unit of the epidermal tonofilaments, was shown to consist of six different polypeptide chains on polyacrylamide-gel systems containing sodium dodecyl sulphate or sodium decyl sulphate with discontinuous gel buffers, but only three chains were seen when a gel system containing sodium dodecyl sulphate with a continuous gel buffer was used. 3. Extraction of the 'keratinized' stratum corneum and the living part of the epidermis with urea buffers at pH 7.6 or 9.0 released 60% of the total dry weight of the tissues in the form of alpha-helical polypeptides. 4. The numbers, relative amounts and properties of the extracted polypeptides were the same as the subunits of prekeratin and thus are derived from the tonofilaments in situ. 5. The subunits of prekeratin and the polypeptides extracted from the living cell layers contained an average of six cysteine residues, but those from the stratum corneum contained an average of three intrachain disulphide bonds. 6. The polypeptide chains aggregated through non-covalent interactions in vitro into filaments that were similar to the tonofilaments. 7. Since the polypeptides could be released from the stratum corneum without breaking covalent bonds, it is concluded that such bonds do not cross-link the tonofilaments and non-fibrous keratohyalin. It is suggested that the tonofilaments and keratohyalin of bovine epidermis are associated by secondary bonding forces.

Amino Acids↗
PubMed1978

Properties of potato lectin and the nature of its glycoprotein linkages.

1. Potato lectin is a glycoprotein that contains about 47% (by weight) l-arabinose, 3% d-galactose and 11% hydroxyproline. It has a monomeric molecular weight of about 50000 and probably exists as a monomer-dimer system in aqueous solution, with the monomer predominating. It has a very high viscosity, which would indicate either that the molecule is very expanded or that it is an elongated ellipsoid. 2. After prolonged proteolytic digestion of a reduced and carboxymethylated derivative of the lectin, a glycopeptide was isolated (of mol.wt. 32000-34000) that included all the carbohydrate and hydroxyproline of the original glycoprotein but less than 30% of the total original amino acid residues. 3. The arabinose of the glycoprotein is present exclusively as the beta-arabinofuranoside and this includes those residues that are directly linked to the hydroxyproline residues of the polypeptide chain. All the arabinose of the glycoprotein is linked to the polypeptide chain through the hydroxyproline residues; the ratio of arabinose to hydroxyproline is 3.4:1. Although alpha-arabinofuranosides are known to be present in arabinans and arabinogalactans, the natural occurrence of beta-arabinofuranosides has not previously been reported. 4. Nine or ten serine residues of the polypeptide chain are substituted with single alpha-galactopyranoside residues that can be removed by the action of alpha-galactosidase from coffee beans but not by a beta-galactosidase. This is the first report of an alpha-galactoside linkage to serine. The effect of alpha-galactosidase is much greater on a glycopeptide from which the arabinose has been already removed, which indicates a steric hindrance of the galactosidase action by adjacent chains of arabinosides. 5. In 0.5m-NaOH (pH13.7), galactose residues were removed from the serine residues of the glycopeptide by a process of beta-elimination. This reaction took place very slowly in the intact glycopeptide but much more rapidly when the arabinofuranoside residues had been removed. This inhibitory effect of the arabinofuranoside residues on the beta-elimination reaction is likely to be due to a negative charge on the hydroxy groups of the adjacent arabinofuranoside residues, which would be ionized at this high pH value. 6. It is suggested that potato lectin may be representative of a class of soluble plant glycoproteins that would include precursors of the cell-wall glycoprotein extensin. If this is the case, extensin should also contain beta-l-arabinofuranosides linked to hydroxyproline and alpha-d-galactopyranosides linked to serine residues of the polypeptide chain.

Amino Acids↗
PubMed1980

Absolute configuration of dolichol.

A derivative of dolichol was formed and then chemically degraded to a small fragment containing the sole centre of asymmetry of the original molecule. Polarimetric comparison of this derivative with a standard prepared from (R)-citronellol showed dolichol to have an S-configuration at C-3. To determine the optical purity of dolichol a diastereoisomeric derivative was prepared and compared with standard diastereoisomers, which could be resolved by high-pressure liquid chromatography. Dolichols from pig liver, human liver and hen oviduct were analysed by this procedure and were all found to be greater than 95% S-configuration.

Aldehydes↗
PubMed1983

The properties of potato (Solanum tuberosum) lectin after deglycosylation by trifluoromethanesulphonic acid.

Potato (Solanum tuberosum) lectin, which is a very highly glycosylated glycoprotein, has been completely deglycosylated by use of the trifluoromethanesulphonic acid reagent described by Edge, Faltnek, Hof, Reichert & Weber [(1981) Analyt. Biochem. 118, 131-137]. This shows that both hydroxyproline-arabinofuranoside and serine-galactopyranoside linkages are hydrolysed. The deglycosylated lectin is still functional and cross-reacts with one component of an anti-(potato lectin) antiserum.

Amino Acids↗