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Biomedical subjects

W C Mahoney

Publications and source records attributed to W C Mahoney.

43 records · Page 3Linked to original sources
PubMed1980

Formation and dissociation of the covalent complexes between trypsin and two homologous inhibitors, alpha 1-antitrypsin and antithrombin III.

The mechanisms by which alpha 1-antitrypsin and antithrombin III inhibit trypsin were investigated by chemical stability studies and amino acid sequence analyses of the enzyme-inhibitor complexes. One-to-one covalently linked complexes were formed between each of the inhibitors and trypsin. The complexes were stable over the course of the experiments at pH 8 or lower, and benzamidine, hydroxylamine, thiols, guanidine, or dodecyl sulfate had no apparent effect on the stability of the complexes. The complexes dissociated slowly at pH 9 or greater. Neither of the inhibitors was active after dissociation from its complex with trypsin. Sequence analysis indicated that no new amino terminus was generated when alpha 1-antitrypsin formed its complex with trypsin, but that two new amino termini were formed in approximately one-to-one ratio when the complex dissociated. This may indicate that alpha 1-antitrypsin contains two inhibitory sites for trypsin in close spatial proximity on the molecule.

Amino Acid Sequence↗
PubMed1980

Complete primary structure of the beta chain from the hemoglobin of a baboon, Papio cynocephalus.

The complete primary structure of the beta chain from the adult hemoglobin of a baboon, Papio cynocephalus, has been determined by automated, Edman degradation of the intact chain and four fragments derived therefrom by specific cleavage reactions. The analysis was facilitated by application of a modified solvent system that permits unambiguous identification, by high-performance liquid chromatography, of the 17 amino acids whose phenylthiohydantoin derivatives are soluble in ethyl acetate. The sequence obtained differs from that of the human beta chain at eight sites, a degree of divergence similar to that observed when human and macaque beta chains are compared. Of the cercopithecoid beta chains whose complete sequences have been determined or inferred from compositions of small peptides, that of P. cynocephalus is most like the beta chain of the gelada baboon, an observation in accord with assessment of a close phylogenetic relationship between the genera Papio and Theropithecus.

Amino Acids↗
PubMed1979

High-yield cleavage of tryptophanyl peptide bonds by o-iodosobenzoic acid.

A new procedure to cleave tryptophanyl peptide bonds in high yield is reported. The method involves treatment of the S-alkylated protein with o-iodosobenzoic acid. The procedure is highly selective for tryptophan and does not modify tyrosine or histidine, but may convert methionine to its sulfoxide derivative. The yields in the cleavage are 70--100%. Tryptophanyl bonds to alanine, glycine, serine, threonine, glutamine, arginine, and S-(pyridylethyl)cysteine are split in nearly quantitative yield, while those preceding isoleucine or valine are split in approximately 70% yield in the proteins examined in this work. The chemical mechanism for tryptophanyl bond cleavage has not been defined, but it is likely that oxidation of the indole ring occurs during the reaction with o-iodosobenzoic acid. Some problems with the quality of commercial preparations of the reagent are discussed.

Amino Acids↗
PubMed1979

Biological activities of the two major components of tunicamycin.

Tunicamycin, an antibiotic that inhibits the transfer of N-acetyglucosamine-1-phosphate from UDP-N-acetylglucosamine to dolichol monophosphate and thereby blocks the formation of protein-carbohydrate linkages of the N-glycosidic type, is not a single compound but a mixture of homologous antibiotics. Two major and eight minor homologs have been identified, all of which possess the ability to inhibit protein glycosylation. The biological activities of the two major components of tunicamycin were investigated and found to differ in their ability to inhibit protein glycosylation and in their effectiveness to inhibit protein synthesis. When completely blocking mannose incorporation into protein, one homolog inhibited protein synthesis by 50% while the other had only a negligible effect. The results demonstrate that differences in biological activity can be discriminated among tunicamycin homologs.

Animals↗
PubMed1979

Complete amino acid sequence of the gamma chain from the major fetal hemoglobin of the pig-tailed macaque, Macaca nemestrina.

The complete primary structure of the gamma chain of the major fetal hemoglobin from the pig-tailed macaque, Macaca nemestrina, was obtained by the automated sequencing of fragments produced by three nonenzymatic cleavage reactions. About two-thirds of the sequence was established from the amino terminus of the intact chain and two of the three fragments produced by cleavage at methionyl residues by cyanogen bromide. Acid clevage at the single aspartyl-prolyl linkage and cleavage at tryptophanyl residues in intact chains yielded the two fragments necessary to complete the sequence. This gamma chain, the first from a nonhuman primate to be sequenced, differes from the human G gamma and A gamma chains at but 4 and 5 positions, respectively. All substitutions are conservative and unlikely to produce alterations in the oxygen-binding properties of tetrameric fetal hemoglobin. Consideration of the data presented herein, together with published observations made on portions of other primate gamma chains, provides some insight into the evolutionary history of the multiple gamma-globin chains observed in several anthropoid primates.

Amino Acid Sequence↗
PubMed1979

Complete sequence of the gamma chain from the fetal hemoglobin of the baboon, Papio cynocephalus.

The amino acid sequence of the hemoglobin gamma chain from a baboon, Papio cynocephalus, was determined by automated sequencing of the intact chain and six fragments generated by specific clevage reactions. The existence of structural heterogeneity at position 75, where both valyl and isoleucyl residues were found, is suggestive of the presence of nonallelic V gamma- and I gamma-chain genes in this species, and further emphasizes the extent to which the genetic basis of hemoglobin production among many higher primates is similar. Comparison of the sequences of those gamma chains from Homo sapiens, Pan troglodytes, Macaca nemestrina and P. cynocephalus that have been well characterized attests to the conservative nature of gamma-chain evolution among the Anthropoidea, the differences in sequence between any two of these chains ranging from none (between the A gamma and G gamma chains of P. troglodytes and H. sapiens) to no more than five (between the V gamma chains of P. cynocephalus and the A gamma chains of H. sapiens).

Amino Acid Sequence↗