ALEKSHUN MN, LEVY SB; Interscience Conference on Antimicrobial Agents and Chemotherapy.

Abstr Intersci Conf Antimicrob Agents Chemother Intersci Conf Antimicrob Agents Chemother. 1999 Sep 26-29; 39: 96 (abstract no. 669).

Tufts Univ. Sch. of Med., Boston, MA.

In Escherichia coli and other members of the Enterobacteriaceae, the chromosomal multiple antibiotic resistance (mar) locus plays an integral role in the response of the organism to toxic environmental conditions. Induction of the marRAB operon, in cells grown in the presence of many structurally unrelated antibiotics and toxic compounds, leads to increased or decreased expression of many other chromosomal genes that comprise the mar regulon. This phenomenon results from inactivation of MarR which negatively regulates the marRAB operon. MarR is a member of a newly recognized family of regulatory proteins. The amino acid sequences of these proteins did not display any obvious homologies to typical DNA binding domains of prokaryotic transcriptional regulators. Therefore, random chemical mutagenesis of plasmids bearing marR was performed in order to define regions of MarR required for DNA binding. Eleven negative complementing trans-dominant mutants were identified. When specified from a plasmid in a wild type host, the mutant proteins associated with, and inactivated, wild type MarR expressed from the chromosome. Many of these mutations affected DNA binding to marO in vitro and were clustered within two regions in MarR that resemble helix-turn-helix (HTH) DNA binding domains of known crystal structure. Mutations in the first putative HTH were more detrimental to MarR function than mutations in the second and suggested that both putative HTHs are required for efficient DNA binding. That a truncated (41 amino acid) form of MarR also had the ability to associate with and inactivate the wild type repressor suggested that the N-terminus of MarR contains the necessary contacts required for the formation of protein multimers. To our knowledge, this is the first study to assign a direct role for the function of particular amino acid sequences for any MarR family member and represents only the second description of dual HTH motifs in a family of prokaryotic transcription factors.

Publication Types:

• Meeting Abstracts

Keywords:

• Base Sequence
• Escherichia coli
• Escherichia coli Proteins
• Genes, Regulator
• In Vitro
• Matrix Attachment Regions
• Mutation
• Operon
• Regulon
• Transcription Factors
• genetics

Other ID:

• GWAIDS0007410

UI: 102244906

From Meeting Abstracts