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Biomedical subjects

B S Hartley

Publications and source records attributed to B S Hartley.

At least 73 records · Page 4Linked to original sources
PubMed1970

The primary structure of alamethicin.

Alamethicin, an antibiotic that can transport cations and induce action potentials in synthetic membranes, is shown to be a cyclic peptide with 18 residues including 7-alpha-aminoisobutyric acid residues, two glutamine residues and one free carboxyl group. The composition indicates microheterogeneity. Alamethicin itself and many peptides derived from it are immune to enzymic digestion, but specific partial acid cleavages have allowed determination of the complete sequence. Diborane reduction has shown that the alpha-carboxyl group of glutamine-18 is free, but the ring is formed by a peptide bond between the imino group of proline-1 and the gamma-carboxyl group of glutamic acid-17. The structure is contrasted with that of other cation-transporting antibiotics. Model building allows a structure that could stack to form a tunnel with a lipophilic exterior and hydrophilic interior and flexible internal arms formed by the pendant C-terminal glutamine residue.

Action Potentials↗
PubMed1970

Amino acid sequences around the disulphide bridges and methionine residues of porcine pepsin.

1. The amino acid sequences around three disulphide bridges and four methionine residues of porcine pepsin were studied by using diagonal electrophoresis methods. 2. Two of the three disulphide bridges were in small loops of five and six residues. The sequence around one of the two half-cystine residues of the third disulphide bridge had a large number of acidic residues. 3. The sequence of a tetrapeptide containing phosphoserine was also determined. 4. Four unique methionine-containing sequences were constructed. The information is sufficient for the determination of the overlaps in the cyanogen bromide fragments of pepsin. 5. The usefulness of diagonal methods in the study of protein structure, the relative positions of cystinyl and methionyl residues in porcine pepsin and the homology between pepsin and rennin are discussed.

Amino Acid Sequence↗
PubMed1969

The use of maleic anhydride for the reversible blocking of amino groups in polypeptide chains.

1. Maleic anhydride was shown to react rapidly and specifically with amino groups of proteins and peptides. Complete substitution of chymotrypsinogen was achieved under mild conditions and the extent of reaction could be readily determined from the spectrum of the maleyl-protein. 2. Maleyl-proteins are generally soluble and disaggregated at neutral pH. Trypsin splits the blocked proteins only at arginine residues and there is frequently selectivity in this cleavage, e.g. in yeast alcohol dehydrogenase and pig glyceraldehyde 3-phosphate dehydrogenase. 3. The group is removed by intramolecular catalysis at acid pH. The half-time was 11-12hr. at 37 degrees at pH3.5 in in-maleyl-lysine or in maleyl-chymotrypsinogen. 4. The unblocking reaction can be used as the basis for a ;diagonal'-electrophoretic separation of lysine peptides and N-terminal peptides, as shown by studies with beta-melanocyte-stimulating hormone.

Alcohol Oxidoreductases↗
PubMed1968

Selective purification of the thiol peptides of myosin.

1. A method for selective purification of thiol peptides is described. Thiol groups in a protein are treated with radioactive cystine by disulphide-thiol interchange. The labelled cystine peptides in a digest can then be fractionated for peptide ;maps'. Performic acid oxidation of paper strips containing the radioactive peptides followed by further ionophoresis yields the purified cysteic acid peptides. 2. The thiol peptides in a peptic digest of cystine-exchanged myosin were purified in this way, and their amino acid sequences were determined. 3. The conclusion that myosin contains at least 16, and probably between 20 and 22, unique thiol sequences indicates that the molecule consists of two chemically equivalent components.

Amino Acid Sequence↗
PubMed1968

Sub-unit structure and specificity of methionyl-transfer-ribonucleic acid synthetase from Escherichia coli.

1. The purification of methionyl-transfer-RNA synthetase from Escherichia coli by a modified technique gives a 16% yield of a protein that appears homogeneous by the criteria of disc gel electrophoresis, ultracentrifugation and end-group analysis. 2. The molecular weight is 96000 and the protein consists of two sub-units of 48000, which appear to be identical. The amino acid composition and thiol content are reported. 3. Kinetic data are reported for analogues of methionine and for pure t-RNA(F) and t-RNA(M), which are respectively the methionine transfer RNA that can exist in the formylmethionyl form and the one that can exist only in the methionyl form. The enzyme binds and acylates both species of transfer RNA identically.

Amino Acid Sequence↗
PubMed1967

A diagonal electrophoretic method for selective purification of methionine peptides.

1. A method is described that selectively purifies methionine peptides from enzymic digests of a protein. The peptides, after paper electrophoresis, are treated on paper with iodoacetamide at acid pH. This specifically converts methionine residues into their sulphonium salts. When the paper is submitted to electrophoresis at right angles to the original direction, the carbamoylmethylmethionine peptides emerge from an undifferentiated diagonal. 2. Heating at neutral pH converts carbamoylmethylmethionine into homoserine and thereby specifically cleaves the peptides. 3. The effect of the modifications on amino acid composition and sequence analyses of the peptides was studied. 4. When the method was applied to a tryptic digest of S-aminoethyl-chymotrypsinogen A, two peptides were selectively purified that had the expected amino acid sequence.

Alkylation↗
PubMed1967

The primary structure of porcine pancreatic elastase. The N-terminus and disulphide bridges.

1. The amino acid composition and N-terminal groups of purified elastase show that it is a single peptide chain of 234 residues. 2. The N-terminal sequence is Val-Val-Gly-Gly-Thr-Glu-. 3. The sequences around the four disulphide bridges were determined by using a ;diagonal' electrophoretic technique. 4. These four bridges are homologous with the four common to bovine trypsin and chymotrypsin. 5. Out of 83 residues of the elastase sequence so far determined, 43 are homologous with similar regions of trypsin and chymotrypsin. 6. The evolutionary ancestry of these enzymes is discussed.

Amino Acid Sequence↗
PubMed1967

The disulphide bridges and soluble tryptic peptides of calf rennin.

1. Cysteic acid peptides from various digests of calf rennin were purified by diagonal paper electrophoresis. 2. The amino acid sequence of these peptides accounts for 38 amino acids around three unique disulphide bridges in rennin. 3. One bridge connects two acidic regions of the chain, one forms a loop of five residues and the other a loop of six residues. 4. These bridges are homologous with those of hog pepsin. 5. Tryptic peptides from the C-terminus of rennin account for 22 residues, 17 of which are homologous with the C-terminus of pepsin. 6. Altogether, sequences accounting for 94 of the 270 residues in rennin are described and the degree of homology with pepsin approximates to 70%.

Amino Acid Sequence↗
PubMed1967

Purification and properties of methionyl-transfer-ribonucleic acid synthetase from Escherichia coli.

1. Methionyl-t-RNA synthetase (where t-RNA denotes ;soluble' or transfer RNA) has been purified to apparent homogeneity from a ribonuclease I-free strain of Escherichia coli. Polyacrylamide-gel electrophoresis of the final product revealed a single band. The purified enzyme catalyses the exchange of 450mumoles of pyrophosphate into ATP/mg. in 15min. at 37 degrees . 2. Methionyl-t-RNA synthetase is specific for the l-isomer of methionine, but appears to catalyse the methionylation of two distinct species of t-RNA, both of which are specific for methionine, but only one of which may be subsequently formylated. 3. The Michaelis constant for l-methionine is 2x10(-4)m in the ATP-PP(i) exchange assay and 2x10(-5)m for the acylation of t-RNA. 4. Gel filtration of both crude and highly purified preparations of methionyl-t-RNA synthetase on Sephadex G-200 indicates that the active species of enzyme has a molecular weight of about 190000. The amino acid composition of the enzyme is similar to those reported for the isoleucine and tyrosine enzymes from E. coli.

Adenosine Triphosphate↗
PubMed1967

The disulphide bridges of bovine chymotrypsinogen B.

The five cystine peptides of chymotrypsinogen B have been isolated as pairs of cysteic acid peptides by the diagonal electrophoretic technique of Brown & Hartley (1963, 1966). The sequences of these peptides have been shown to be very similar to those of chymotrypsinogen A, and indicate that both zymogens have the same pattern of disulphide bridges. The determination of the sequence of residues 14-21 in chymotrypsinogen B has shown that residue 18 differs in the chymotrypsinogens from the corresponding residue in trypsinogen. Eight differences between chymotrypsinogens A and B are found in sequences accounting for 72 of the 245 residues.

Journal Article↗