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首页> 外文期刊>Journal of Experimental Botany >Structure–function analysis of the NB-ARC domain of plant disease resistance proteins
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Structure–function analysis of the NB-ARC domain of plant disease resistance proteins

机译：植物抗病蛋白NB-ARC结构域的结构-功能分析

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摘要

Resistance (R) proteins in plants are involved in pathogen recognition and subsequent activation of innate immune responses. Most resistance proteins contain a central nucleotide-binding domain. This so-called NB-ARC domain consists of three subdomains: NB, ARC1, and ARC2. The NB-ARC domain is a functional ATPase domain, and its nucleotide-binding state is proposed to regulate activity of the R protein. A highly conserved methionine–histidine–aspartate (MHD) motif is present at the carboxy-terminus of ARC2. An extensive mutational analysis of the MHD motif in the R proteins I-2 and Mi-1 is reported. Several novel autoactivating mutations of the MHD invariant histidine and conserved aspartate were identified. The combination of MHD mutants with autoactivating hydrolysis mutants in the NB subdomain showed that the autoactivation phenotypes are not additive. This finding indicates an important regulatory role for the MHD motif in the control of R protein activity. To explain these observations, a three-dimensional model of the NB-ARC domain of I-2 was built, based on the APAF-1 template structure. The model was used to identify residues important for I-2 function. Substitution of the selected residues resulted in the expected distinct phenotypes. Based on the model, it is proposed that the MHD motif fulfils the same function as the sensor II motif found in AAA+ proteins (ATPases associated with diverse cellular activities)—co-ordination of the nucleotide and control of subdomain interactions. The presented 3D model provides a framework for the formulation of hypotheses on how mutations in the NB-ARC exert their effects.
机译：植物中的抗性（R）蛋白与病原体识别和随后的先天免疫应答激活有关。大多数抗性蛋白包含一个中央核苷酸结合结构域。所谓的NB-ARC域由三个子域组成：NB，ARC1和ARC2。 NB-ARC结构域是一个功能性ATP酶结构域，并提出其核苷酸结合状态可调节R蛋白的活性。 ARC2的羧基末端存在高度保守的蛋氨酸-组氨酸-天冬氨酸（MHD）基序。据报道，对R蛋白I-2和Mi-1中的MHD基序进行了广泛的突变分析。 MHD不变组氨酸和保守的天冬氨酸的几个新的自动激活突变被确定。 MHD突变体与NB子域中的自激活水解突变体的组合显示自激活表型不是累加的。该发现表明MHD基序在控制R蛋白活性中的重要调节作用。为了解释这些发现，基于APAF-1模板结构，构建了I-2的NB-ARC域的三维模型。该模型用于鉴定对I-2功能重要的残基。所选残基的取代产生预期的不同表型。基于该模型，建议MHD基序发挥与AAA +蛋白（与多种细胞活性相关的ATPase）中的sensor II基序相同的功能-核苷酸的配位和亚域相互作用的控制。提出的3D模型为NB-ARC中的突变如何发挥作用的假设提出了框架。

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