title: The tib adherence locus of enterotoxigenic Escherichia coli is regulated by cyclic AMP receptor protein.
abstract: Enterotoxigenic Escherichia coli (ETEC) is a Gram-negative enteric pathogen that causes profuse watery diarrhea through the elaboration of heat-labile and/or heat-stable toxins. Virulence is also dependent upon the expression of adhesive pili and afimbrial adhesins that allow the pathogen to adhere to the intestinal epithelium or mucosa. Both types of enterotoxins are regulated at the level of transcription by cyclic AMP (cAMP) receptor protein (CRP). To further our understanding of virulence gene regulation, an in silico approach was used to identify putative CRP binding sites in the genome of H10407 (O78:H11), an ETEC strain that was originally isolated from the stool of a Bangledeshi patient with cholera-like symptoms circa 1971. One of the predicted binding sites was located within an intergenic region upstream of tibDBCA. TibA is an autotransporter and afimbrial adhesin that is glycosylated by TibC. Expression of the TibA glycoprotein was abolished in an H10407 crp mutant and restored when crp was provided in trans. TibA-dependent aggregation was also abolished in a cyaA::kan strain and restored by addition of exogenous cAMP to the growth medium. DNase I footprinting confirmed that the predicted site upstream of tibDBCA is bound by CRP. Point mutations within the CRP binding site were found to abolish or significantly impair CRP-dependent activation of the tibDB promoter. Thus, these studies demonstrate that CRP positively regulates the expression of the glycosylated afimbrial adhesin TibA through occupancy of a binding site within tibDBp.
authors.affiliation: Department of Microbiology and Immunology, University of Miami Miller School of Medicine, P.O. Box 016960 (R-138), Miami, FL 33101, USA.
authors.forename: Shirley M
authors.initials: SM
authors.lastname: Espert
authors.forename: Eric A
authors.initials: EA
authors.lastname: Elsinghorst
authors.forename: George P
authors.initials: GP
authors.lastname: Munson
mesh_terms: D018829:Adhesins, Bacterial / Q000096:biosynthesis*; D018830:Adhesins, Escherichia coli; D001422:Bacterial Adhesion; D001459:Bangladesh; D001665:Binding Sites; D018983:DNA Footprinting; D004269:DNA, Bacterial / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D054307:Enterotoxigenic Escherichia coli / Q000235:genetics* / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000382:microbiology; D029968:Escherichia coli Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism*; D005243:Feces / Q000382:microbiology; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D056426:Genetic Loci; D006801:Humans; D017354:Point Mutation; D011485:Protein Binding; D011953:Receptors, Cyclic AMP / Q000235:genetics / Q000378:metabolism*; D037521:Virulence Factors / Q000096:biosynthesis*
chemical_list: D018829:Adhesins, Bacterial; D018830:Adhesins, Escherichia coli; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D011953:Receptors, Cyclic AMP; C557497:TibA protein, E coli; D037521:Virulence Factors; C047947:cyclic AMP receptor protein, E coli