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DNA binding of Escherichia coli arginine repressor mutants altered in oligomeric state
Author(s) -
Chen SheauHu,
Merican Amir F.,
Sherratt David J.
Publication year - 1997
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1997.4301791.x
Subject(s) - repressor , biology , arginine , random hexamer , escherichia coli , mutant , trimer , dna , binding site , wild type , biochemistry , microbiology and biotechnology , amino acid , gene , chemistry , dimer , gene expression , organic chemistry
The Escherichia coli arginine repressor (ArgR) controls expression of the arginine biosynthetic genes and acts as an accessory protein in Xer site‐specific recombination at cer and related plasmid recombination sites. The hexameric wild‐type protein shows L ‐arginine‐dependent DNA binding. In this work, ArgR mutants that are defective in trimer–trimer interactions and bind DNA as trimers in an L ‐arginine‐independent manner are isolated and characterized. Whereas the wild‐type ArgR hexamer exhibits high‐affinity binding to two repeated ARG boxes separated by 3 bp (each ARG box containing two identical dyad symmetrical 9 bp half‐sites), the trimeric mutants bind to and footprint three adjacent half‐sites of this ‘idealized’ substrate. Trimeric ArgR is impaired in its ability to repress the arginine biosynthetic genes and in Xer site‐specific recombination. In the absence of L ‐arginine, residual wild‐type ArgR‐binding occurs as trimers. The binding of an N‐terminal 77‐amino‐acid DNA‐binding domain to idealized ARG boxes is also characterized.