Open AccessEscherichia coli metR mutants that produce a MetR activator protein with an altered homocysteine response
Author(s) -
Kyna A. Byerly,
Mark L. Urbanowski,
George V. Stauffer
Publication year - 1990
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.172.6.2839-2843.1990
Subject(s) - biology , complementation , escherichia coli , lac operon , activator (genetics) , microbiology and biotechnology , mutant , gene , gene expression , regulation of gene expression , genetics
Using an Escherichia coli lac deletion strain lysogenized with a lambda phage carrying a metH-lacZ gene fusion, we isolated trans-acting mutations that result in simultaneous 4- to 6-fold-elevated metH-lacZ expression, 5- to 22-fold-lowered metE-lacZ expression, and 9- to 20-fold-elevated metR-lacZ expression. The altered regulation of these genes occurs in the presence of high intracellular levels of homocysteine, a methionine pathway intermediate which normally inhibits metH and metR expression and stimulates metE expression. P1 transductions and complementation tests indicate that the mutations are in the metR gene. Our data suggest that the mutations result in an altered MetR activator protein that has lost the ability to use homocysteine as a modulator of gene expression.