Identifying regulators of transcription in an obligate intracellular pathogen: a metal-dependent repressor in Chlamydia trachomatis.
A prominent feature exhibited by Chlamydia trachomatis growing in an iron-limiting environment is a differential pattern of protein expression. In many bacteria, iron-responsive proteins are regulated at the level of transcription by a family of repressors resembling the Escherichia coli ferric uptake regulator (Fur) protein. Although the chlamydial genome sequencing project did not unveil an obvious Fur homologue, a detailed examination indicated five unassigned open reading frames (ORFs) that would encode products with limited sequence homology to Fur. In this report, each chlamydial ORF was engineered in E. coli, and recombinant proteins were examined for functional characteristics resembling Fur. A Fur-specific polyclonal antiserum revealed that the protein encoded by ORF CT296 shares antigenic cross-recognition. Moreover, this protein forms dimers in solution in a fashion analogous to E. coli Fur. Further studies confirmed that the product of ORF CT296 is able to (i) complement Fur activity in a mutant strain of E. coli; and (ii) specifically bind to a 19 bp consensus sequence found in promoters of iron-regulated genes in E. coli. We propose a designation of dcrA (divalent cation-dependent regulator A) for ORF CT296, which encodes a protein distantly related to E. coli Fur. DcrA represents the first repressor described for this obligate intracellular bacterium.
Wyllie
S
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Departments of Microbiology and Pathology, James H. Quillen College of Medicine, Box 70579, East Tennessee State University, Johnson City, TN 37614-0579, USA.
Raulston
J E
JE
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D002692:Chlamydia trachomatis / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D003429:Cross Reactions; D004926:Escherichia coli / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D008565:Membrane Proteins; D008670:Metals / Q000378:metabolism*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
D001426:Bacterial Proteins; C432145:DcrA protein, Chlamydia trachomatis; D008565:Membrane Proteins; D008670:Metals; D012097:Repressor Proteins; C085429:dcrA protein, Desulfovibrio vulgaris; C068477:ferric uptake regulating proteins, bacterial