Structure of HrcQB-C, a conserved component of the bacterial type III secretion systems

AUTOR(ES)

Fadouloglou, Vasiliki E.

FONTE

National Academy of Sciences

RESUMO

Type III secretion systems enable plant and animal bacterial pathogens to deliver virulence proteins into the cytosol of eukaryotic host cells, causing a broad spectrum of diseases including bacteremia, septicemia, typhoid fever, and bubonic plague in mammals, and localized lesions, systemic wilting, and blights in plants. In addition, type III secretion systems are also required for biogenesis of the bacterial flagellum. The HrcQB protein, a component of the secretion apparatus of Pseudomonas syringae with homologues in all type III systems, has a variable N-terminal and a conserved C-terminal domain (HrcQB-C). Here, we report the crystal structure of HrcQB-C and show that this domain retains the ability of the full-length protein to interact with other type III components. A 3D analysis of sequence conservation patterns reveals two clusters of residues potentially involved in protein–protein interactions. Based on the analogies between HrcQB and its flagellum homologues, we propose that HrcQB-C participates in the formation of a C-ring-like assembly.

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