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Biomedical subjects

M Riley

Publications and source records attributed to M Riley.

At least 127 records · Page 7Linked to original sources
PubMed1978

Relationship between gene function and gene location in Escherichia coli.

Genes of Escherichia coli were grouped according to the "biochemical relatedness" of the enzymes they specifiy, using two schemes to determine relatedness: similarity of reaction or similarity of reactants. The tendency of biochemically related genes as so defined to lie approximately 90 degrees or 180 degrees from one another on the circular genetic map was analyzed statistically. Of the classes analyzed, only the genes for the enzymes of glucose catabolism showed a significant departure from random distribution in this respect. The glucose catabolism genes showed a pronounced tendency to lie either 90 degrees of 180 degrees from one another (P = ca. 10(-9)), and, furthermore, most of these genes were found to lie in only four gene clusters on the E. coli genome. The significance of this observation is discussed in relation to evolutionary mechanisms and to mechanisms of gene expression.

Amino Acids↗
PubMed1976

Amino acid compositions of the subunit chains of lamprey fibrinogen. Evolutionary significance of some structural anomalies.

Our original objective in studying lamprey fibrinogen was embodied in the notion that the proteins of this ancient vertebrate might themselves by more primitive. As such, it was possible that the subunits of lamprey fibrinogen might have been more similar, one to another, than is the case in higher vertebrates, or even identical. Amino acid analysis of the individual polypeptide chains indicates, however, that the alpha, beta and gamma-chains are instead more dissimilar from each other than are the corresponding chains from human fibrinogen. This finding was somewhat surprising because regions of homology have been detected recently among those three chains when isolated from human fibrinogen, suggesting that all three chains have indeed descended from a common ancestor. The paradox is especially evidenced by the unusual amino acid composition of the lamprey alpha-chain, 45% of which is composed of glycine, serine and threonine. This unusual amino acid distribution may be involved in the anomalous behavior of these chains on sodium dodecyl sulfate polyacrylamide gel electrophoresis.

Amino Acids↗
PubMed1975

Proposal concerning mechanism of evolution of the genome of Escherichia coli.

Many pairs of genes whose gene products are functionally related lie either 90 degrees or 180 degrees apart on the circular map of the E. coli chromosome. A mechanism of evolution is proposed that involves two sequential duplications of an ancestral genome, followed by mutation and divergence of function of replicate genes.

Biological Evolution↗
PubMed1973

The reaction of protein amino groups with methyl 5-iodopyridine-2-carboximidate. A possible general method of preparing isomorphous heavy-atom derivatives of proteins.

1. The synthesis of methyl 5-iodopyridine-2-carboximidate and its reaction with amino groups of model compounds and performic acid-oxidized insulin are described. The reagent was designed to introduce heavy atoms into specific sites in proteins. 2. Specific reaction with the amino groups of oxidized insulin can be achieved under reasonably mild conditions giving rise to the corresponding N-monosubstituted amidines. 3. The extent of reaction of this reagent with protein amino groups can be readily determined by difference spectroscopy. Modification of lysine residues inhibits tryptic cleavage at such residues, and this can be of assistance in establishing the site of modification in the primary structure. 4. Evidence is presented to show that methyl 5-iodopyridine-2-carboximidate can react specifically, at pH5.0, with the aromatic amino group of 3-amino-l-tyrosine; the final product of this reaction is a 2-arylbenzoxazole. 5. The use of this reagent as a general method for preparing heavy-atom isomorphous derivatives of proteins is discussed.

Amidines↗
PubMed1970

The reversible reaction of protein amino groups with exo-cis-3,6-endoxo-delta-tetrahydrophthalic anhydride.

1. The reaction of exo-cis-3,6-endoxo-Delta(4)-tetrahydrophthalic anhydride with amino groups of model compounds and lysozyme is described. 2. Reaction with the in-amino group of N(alpha)-acetyl-l-lysine amide gives rise to two diastereoisomeric products; at acid pH the free amino group is liberated with anchimeric assistance by the neighbouring protonated carboxyl group with a half-time of 4-5h at pH3.0 and 25 degrees C. 3. The amino groups of lysozyme can be completely blocked, with total loss of enzymic activity. Dialysis at pH3.0 results in complete recovery of the native primary and tertiary structure of lysozyme and complete return of catalytic activity. 4. The specificity of reaction of this and other anhydrides with amino groups in proteins is discussed.

Amino Acids↗