Open AccessFunctional characterization of NopT 1 and NopT 2, two type III effectors of B radyrhizobium japonicum
Author(s) -
Fotiadis Christos T.,
Dimou Maria,
Georgakopoulos Dimitrios G.,
Katinakis Panagiotis,
Tampakaki Anastasia P.
Publication year - 2012
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.2011.02466.x
Subject(s) - effector , bradyrhizobium japonicum , proteases , protease , cysteine protease , papain , bradyrhizobium , catalytic triad , biochemistry , cysteine , escherichia coli , biology , proteolysis , chemistry , bacteria , serine , enzyme , symbiosis , genetics , rhizobiaceae , gene , rhizobium
NopT 1 and NopT 2, putative type III effectors from the plant symbiotic bacterium B radyrhizobium japonicum , are predicted to belong to a family of YopT / AvrPphB effectors, which are cysteine proteases. In the present study, we showed that both NopT 1 and NopT 2 indeed possess cysteine protease activity. When overexpressed in E scherichia coli , both NopT 1 and NopT 2 undergo autoproteolytic processing which is largely abolished in the presence of E ‐64, a papain family‐specific inhibitor. Mutations of NopT 1 disrupting either the catalytic triad or the putative autoproteolytic site reduce or markedly abolish the protease activity. Autocleavage likely occurs between residues K 48 and M 49, though another potential cleavage site is also possible. NopT 1 also elicitis HR ‐like cell death when transiently expressed in tobacco plants and its cysteine protease activity is essential for this ability. In contrast, no macroscopic symptoms were observed for NopT 2. Furthermore, mutational analysis provided evidence that NopT 1 may undergo acylation inside plant cells and that this would be required for its capacity to elicit HR ‐like cell death in tobacco.