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Publication Abstract from PubMed

Secretins are among the largest bacterial outer membrane proteins known. Here we report the crystal structure of the periplasmic N-terminal domain of GspD (peri-GspD) from the type 2 secretion system (T2SS) secretin in complex with a nanobody, the VHH domain of a heavy-chain camelid antibody. Two different crystal forms contained the same compact peri-GspD:nanobody heterotetramer. The nanobody contacts peri-GspD mainly via CDR3 and framework residues. The peri-GspD structure reveals three subdomains, with the second and third subdomains exhibiting the KH fold which also occurs in ring-forming proteins of the type 3 secretion system. The first subdomain of GspD is related to domains in phage tail proteins and outer membrane TonB-dependent receptors. A dodecameric peri-GspD model is proposed in which a solvent-accessible beta strand of the first subdomain interacts with secreted proteins and/or T2SS partner proteins by beta strand complementation.

Crystal structure of the N-terminal domain of the secretin GspD from ETEC determined with the assistance of a nanobody.,Korotkov KV, Pardon E, Steyaert J, Hol WG Structure. 2009 Feb 13;17(2):255-65. PMID:19217396^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.