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In vivo and in vitro mutants of FNR the anaerobic transcriptional regulator of E.coli
Author(s) -
Sharrocks Andrew D.,
Green Jeffrey,
Guest John R.
Publication year - 1990
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(90)81248-m
Subject(s) - mutant , regulator , in vivo , in vitro , transcriptional regulation , escherichia coli , chemistry , anaerobic exercise , microbiology and biotechnology , biology , biochemistry , gene , genetics , gene expression , physiology
FNR regulates the expression of target genes in response to anaerobiosis. It resembles the catabolite gene activator or cAMP‐receptor protein (CRP) except for the presence of an N‐terminal cysteine cluster, which may form a redox‐sensing iron‐binding site. Site‐directed mutagenesis has shown that 3 of the 4 cysteine residues in the N‐terminal cluster (Cys‐20, ‐23 and ‐29, but not Cys‐16) and the only other cysteine residue (Cys‐122), are essential for the normal activation and repression of PNR‐dependent promoters. Deletion of residues Pro‐3‐Arg‐9 (inclusive) had no effect, but FNR was inactivated by a frameshift extending through the C‐terminal DNA‐binding domain. Four independent in vivo mutants contained identical Gly‐96→Asp substitutions, which may inactivate FNR by distorting a sharp turn between β‐strands in the predicted structure.