On the Evolution of β -galactosidase

The amino acid sequence of β -galactosidase (β -D-galactoside galactohydrolase, EC 3.2.1.23) has been compared to itself and to other proteins. Two segments, each of about 380 amino acids, comprising the first three-fourths of the polypeptide chain, were found to be very similar to each other. It is...

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Veröffentlicht in:	Proceedings of the National Academy of Sciences - PNAS 1978-01, Vol.75 (1), p.113-116
Hauptverfasser:	Hood, J. Myron, Fowler, Audree V., Zabin, Irving
Format:	Artikel
Sprache:	eng
Schlagworte:	Amino Acid Sequence Amino acids Bacterial Proteins - genetics beta-Galactosidase - genetics Biochemistry Biological Evolution Enzyme Repression Escherichia coli - enzymology Escherichia coli - genetics Evolution Galactosidases - genetics Genes, Regulator Lac operon Lactose - metabolism Operon Operons Regional identity Repressor proteins rev genes Tetrahydrofolate Dehydrogenase - genetics
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Zusammenfassung:	The amino acid sequence of β -galactosidase (β -D-galactoside galactohydrolase, EC 3.2.1.23) has been compared to itself and to other proteins. Two segments, each of about 380 amino acids, comprising the first three-fourths of the polypeptide chain, were found to be very similar to each other. It is concluded that they are homologous. The carboxyl-terminal fourth has a high percentage of amino acid identities with dihydrofolate reductase of Escherichia coli, suggesting these sequences also are homologous. A model for the origin of β -galactosidase is presented. The overall similarity of β -galactosidase to lac repressor does not appear to be significant.
ISSN:	0027-8424 1091-6490
DOI:	10.1073/pnas.75.1.113