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The arsD gene encodes a second trans ‐acting regulatory protein of the plasmid‐encoded arsenical resistance operon
Author(s) -
Wu Jianhua,
Rosen Barry P.
Publication year - 1993
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 - 10.1111/j.1365-2958.1993.tb01605.x
Subject(s) - operon , biology , plasmid , gene , genetics , escherichia coli
Summary The plasmid‐encoded arsenical resistance ( ars ) operon produces resistance to trivalent and pentavalent salts of arsenic and antimony. The first gene in the operon, arsR , was previously shown to encode a repressor protein. A newly identified gene, arsD , is shown here to encode a regulatory protein, the ArsD protein. The gene was identified by construction of an in‐frame fusion between the C ‐terminally truncated arsD gene and the coding region for the mature form of β‐lactamase ( blaM ). The native arsD gene product was overexpressed and radioactively labelled as a 13kDa polypeptide. A frameshift mutation within the arsD gene resulted in elevated levels of expression of downstream ars genes. Co‐expression of a wild‐type arsD gene in trans with the operon containing the mutated arsD gene reduced expression of the downstream genes to wild‐type levels. The presence of the arsD gene had no effect on the basal level of operon expression set by the arsR gene product, and the repression produced by the arsD gene product was not affected by inducers of the operon. The results indicate that the ArsD protein is an inducer‐independent trans ‐acting regulatory protein.