Show simple item record

dc.contributor.advisorPayne, Shelley M.en
dc.creatorMey, Alexandra Rebeccaen
dc.date.accessioned2008-08-28T21:34:50Zen
dc.date.available2008-08-28T21:34:50Zen
dc.date.issued2002en
dc.identifierb57165634en
dc.identifier.urihttp://hdl.handle.net/2152/785en
dc.descriptiontexten
dc.description.abstractVibrio cholerae has multiple iron transport systems, one of which involves heme uptake through the outer membrane receptor HutA. This study demonstrates that V. cholerae encodes two additional TonB-dependent heme receptors, HutR and HasR. HutR has significant homology to HutA and to other bacterial outer membrane heme receptors, and the role of HutR in hemin utilization and its localization in the outer membrane were confirmed. The hutR gene was co-transcribed with the upstream gene ptrB, and expression from the ptrB promoter was negatively regulated by iron. HasR is most similar to the hemophore-utilizing heme receptors from Pseudomonas aeruginosa and Serratia marcescens. A mutant defective in all three heme receptors was unable to utilize hemin as an iron source. HutA and HutR functioned with either V. cholerae TonB1 or TonB2. In contrast, hemin uptake through HasR was TonB2- dependent. Efficient utilization of hemoglobin as an iron source required HutA and TonB1. The triple heme receptor mutant exhibited no defect in its ability to compete with its Vib- parental strain in an infant mouse model of infection, indicating that additional iron sources are present in vivo. V. cholerae utilized heme derived from marine invertebrate hemoglobins, suggesting that heme may be available to V. cholerae growing in the marine environment. Although E. coli TonB and V. cholerae TonB1 exhibit different specificities for outer membrane receptors, these TonB proteins are similar enough that functional chimeras can be created between them. The activities of the chimeric TonB proteins demonstrated that the C-terminal one-third of TonB constitutes a functional domain responsible for receptor specificity. A Pro238Thr substitution in V. cholerae TonB1 resulted in the ability of TonB1 to recognize a wider range of receptors, indicating that very C-terminal end of TonB1 determines receptor specificity. Domain-switching experiments between E. coli ChuA and V. cholerae HutA showed that the TonB box heptapeptide at the Nterminus of these receptors does not contain specificity determinants. Instead, specificity was controlled by the residue immediately preceding the TonB box. Taken together, these data suggest that functional interactions take place between the C-terminus of TonB and the very N-terminal domain of TonB-dependent receptors.
dc.format.mediumelectronicen
dc.language.isoengen
dc.rightsCopyright is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works.en
dc.subject.lcshVibrio choleraeen
dc.subject.lcshHemeen
dc.titleHeme utilization in Vibrio cholerae and analysis of domains involved in the specificity of TonB for TonB-dependent receptorsen
dc.description.departmentBiological Sciences, School ofen
dc.identifier.oclc56818203en
dc.identifier.proqst3115503en
dc.type.genreThesisen
thesis.degree.departmentBiological Sciences, School ofen
thesis.degree.disciplineEcology, Evolution, and Behavioren
thesis.degree.grantorThe University of Texas at Austinen
thesis.degree.levelDoctoralen
thesis.degree.nameDoctor of Philosophyen


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record