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Binding affects the tertiary and quaternary structures of the Shigella translocator protein IpaB and its chaperone IpgC.
Adam, Philip R; Patil, Mrinalini K; Dickenson, Nicholas E; Choudhari, Shyamal; Barta, Michael; Geisbrecht, Brian V; Picking, Wendy L; Picking, William D.
Afiliação
  • Adam PR; Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK 74078, USA.
Biochemistry ; 51(19): 4062-71, 2012 May 15.
Article em En | MEDLINE | ID: mdl-22497344
ABSTRACT
Shigella flexneri uses its type III secretion system (T3SS) to promote invasion of human intestinal epithelial cells as the first step in causing shigellosis, a life-threatening form of dysentery. The Shigella type III secretion apparatus (T3SA) consists of a basal body that spans the bacterial envelope and an exposed needle that injects effector proteins into target cells. The nascent Shigella T3SA needle is topped with a pentamer of the needle tip protein invasion plasmid antigen D (IpaD). Bile salts trigger recruitment of the first hydrophobic translocator protein, IpaB, to the tip complex where it senses contact with a host membrane. In the bacterial cytoplasm, IpaB exists in a complex with its chaperone IpgC. Several structures of IpgC have been determined, and we recently reported the 2.1 Å crystal structure of the N-terminal domain (IpaB(74.224)) of IpaB. Like IpgC, the IpaB N-terminal domain exists as a homodimer in solution. We now report that when the two are mixed, these homodimers dissociate and form heterodimers having a nanomolar dissociation constant. This is consistent with the equivalent complexes copurified after they had been co-expressed in Escherichia coli. Fluorescence data presented here also indicate that the N-terminal domain of IpaB possesses two regions that appear to contribute additively to chaperone binding. It is also likely that the N-terminus of IpaB adopts an alternative conformation as a result of chaperone binding. The importance of these findings within the functional context of these proteins is discussed.
Assuntos

Texto completo: 1 Base de dados: MEDLINE Assunto principal: Proteínas de Bactérias / Chaperonas Moleculares Idioma: En Ano de publicação: 2012 Tipo de documento: Article

Texto completo: 1 Base de dados: MEDLINE Assunto principal: Proteínas de Bactérias / Chaperonas Moleculares Idioma: En Ano de publicação: 2012 Tipo de documento: Article