Open AccessInternal homologies in the two aspartokinase-homoserine dehydrogenases of Escherichia coli K-12.
Author(s) -
Pascual Ferrara,
Nathalie Duchange,
Mario M. Zakin,
Georges N. Cohen
Publication year - 1984
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.81.10.3019
Subject(s) - amino acid , threonine , escherichia coli , biochemistry , methionine , biology , homoserine , homology (biology) , peptide sequence , gene , chemistry , genetics , enzyme , serine , quorum sensing , virulence
In Escherichia coli, AK I- HDH I and AK II- HDH II are two bifunctional proteins, derived from a common ancestor, that catalyze the first and third reactions of the common pathway leading to threonine and methionine. An extensive amino acid sequence comparison of both molecules reveals two main features on each of them: (i) two segments, each of about 130 amino acids, covering the first one-third of the polypeptide chain, are similar to each other and (ii) two segments, each of about 250 amino acids and covering the COOH-terminal 500 amino acids also present a significant homology. These findings suggest that these two regions may have evolved independently of each other by a process of gene duplication and fusion previous to the appearance of an ancestral aspartokinase-homoserine dehydrogenase molecule.