Characterization of the Type III Effector VOPA from Vibrio Parahaemolyticus

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Title: Characterization of the Type III Effector VOPA from Vibrio Parahaemolyticus
Author: Trosky, Jennifer E.
Abstract: Vibrio parahaemolyticus is a marine bacterium and causative agent of gastroenteritis associated with the consumption of contaminated seafood . It is endemic to Southeast Asia and is the leading cause of gastroenteritis in Japan . Sequencing of the Vibrio parahaemolyticus genome revealed the presence of a type III secretion system (TTSS ) encoded within a pathogenicity island . Within this pathogenicity island a homologue of the Yersinia type III effector YopJ was found and is referred to as VopA (Vibrio outer protein A ) . The founding member of the family , YopJ from Yersinia spp . , inhibits the MAPK and the NFκB signaling cascades within the host cell , thereby inhibiting the host's innate immune response . Recently our lab elucidated the mechanism of YopJ's inhibition by demonstrating that YopJ acetylates MKKs and inhibits kinase activation by blocking phosphorylation (1 ) . The molecular characterization of VopA has focused on its effect on signaling pathways . In contrast to YopJ , VopA only inhibits MAPK signaling and shows no effect on the NFκB pathway in mammalian cells . In addition , VopA , like YopJ , utilizes an evolutionary conserved mechanism for inhibition of signaling which is demonstrated by VopA's ability to inhibit MAPK signaling in Saccharo ces cerevisiae . I have shown that VopA is an acetyltransferase targets the MKK within the MAPK cascade revealing an activity similar to YopJ's . Through mass spectrometric analysis , I found that VopA modifies MKK on four different residues . Three of the residues , S207 , K210 , and T211 , that are located in the activation loop , are the same residues modified by YopJ . The fourth residue , K172 , is only modified by VopA and is a conserved lysine in the catalytic loop of MKKs that is required for ATP binding . I have shown that VopA's modification of this residue disrupts ATP binding and allows for the inhibition of an activated kinase .
URI: http : / /hdl .handle .net /2152 .5 /770
Date: 2007-12-18

Citation

Characterization of the Type III Effector VOPA from Vibrio Parahaemolyticus. Graduate School of Biomedical Sciences. Available electronically from http : / /hdl .handle .net /2152 .5 /770 .

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