Wang Ching-I A, Guncar Gregor, Forwood Jade K, Teh Trazel, Catanzariti Ann-Maree, Lawrence Gregory J, Loughlin Fionna E, Mackay Joel P, Schirra Horst Joachim, Anderson Peter A, Ellis Jeffrey G, Dodds Peter N, Kobe Bostjan
School of Molecular and Microbial Sciences, University of Queensland, Brisbane, Queensland, Australia.
Plant Cell. 2007 Sep;19(9):2898-912. doi: 10.1105/tpc.107.053611. Epub 2007 Sep 14.
The gene-for-gene mechanism of plant disease resistance involves direct or indirect recognition of pathogen avirulence (Avr) proteins by plant resistance (R) proteins. Flax rust (Melampsora lini) AvrL567 avirulence proteins and the corresponding flax (Linum usitatissimum) L5, L6, and L7 resistance proteins interact directly. We determined the three-dimensional structures of two members of the AvrL567 family, AvrL567-A and AvrL567-D, at 1.4- and 2.3-A resolution, respectively. The structures of both proteins are very similar and reveal a beta-sandwich fold with no close known structural homologs. The polymorphic residues in the AvrL567 family map to the surface of the protein, and polymorphisms in residues associated with recognition differences for the R proteins lead to significant changes in surface chemical properties. Analysis of single amino acid substitutions in AvrL567 proteins confirm the role of individual residues in conferring differences in recognition and suggest that the specificity results from the cumulative effects of multiple amino acid contacts. The structures also provide insights into possible pathogen-associated functions of AvrL567 proteins, with nucleic acid binding activity demonstrated in vitro. Our studies provide some of the first structural information on avirulence proteins that bind directly to the corresponding resistance proteins, allowing an examination of the molecular basis of the interaction with the resistance proteins as a step toward designing new resistance specificities.
植物抗病性的基因对基因机制涉及植物抗性（R）蛋白直接或间接识别病原体无毒（Avr）蛋白。亚麻锈菌（Melampsora lini）的AvrL567无毒蛋白与相应的亚麻（Linum usitatissimum）L5、L6和L7抗性蛋白直接相互作用。我们分别以1.4埃和2.3埃的分辨率确定了AvrL567家族两个成员AvrL567 - A和AvrL567 - D的三维结构。这两种蛋白质的结构非常相似，呈现出一种β - 折叠结构，且没有已知的紧密结构同源物。AvrL567家族中的多态性残基位于蛋白质表面，与R蛋白识别差异相关的残基多态性导致表面化学性质发生显著变化。对AvrL567蛋白中单个氨基酸取代的分析证实了个别残基在赋予识别差异方面的作用，并表明特异性是由多个氨基酸接触的累积效应产生的。这些结构还为AvrL567蛋白可能的病原体相关功能提供了见解，体外实验证明其具有核酸结合活性。我们的研究提供了一些关于直接与相应抗性蛋白结合的无毒蛋白的首批结构信息，有助于研究与抗性蛋白相互作用的分子基础，从而朝着设计新的抗性特异性迈进。
