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Science Signalin:植物G蛋白能够独立于GDP-GTP交换而发挥功能

已有 570 次阅读 2019-12-16 15:53 |个人分类:每日摘要|系统分类:论文交流

Nucleotide exchange–dependent and nucleotide exchange–independent functions of plant heterotrimeric GTP-binding proteins


First author: Natsumi Maruta; Affiliations: University of Queensland (昆士兰大学): Brisbane, Australia

Corresponding author: Jose R. Botella


Heterotrimeric guanine nucleotide–binding proteins (G proteins), which are composed of α, β, and γ subunits, are versatile (多功能的), guanine nucleotide–dependent, molecular on-off switches. In animals and fungi, the exchange of GDP for GTP on Gα controls G protein activation and is crucial for normal cellular responses to diverse extracellular signals. The model plant Arabidopsis thaliana has a single canonical Gα subunit, AtGPA1. We found that, in planta, the constitutively active, GTP-bound AtGPA1(Q222L) mutant and the nucleotide-free AtGPA1(S52C) mutant interacted with Gβγ1 and Gβγ2 dimers with similar affinities, suggesting that G protein heterotrimer formation occurred independently of nucleotide exchange. In contrast, AtGPA1(Q222L) had a greater affinity than that of AtGPA1(S52C) for Gβγ3, suggesting that the GTP-bound conformation of AtGPA1(Q222L) is distinct and tightly associated with Gβγ3. Functional analysis of transgenic lines expressing either AtGPA1(S52C) or AtGPA1(Q222L) in the gpa1-null mutant background revealed various mutant phenotypes that were complemented by either AtGPA1(S52C) or AtGPA1(Q222L). We conclude that, in addition to the canonical GDP-GTP exchange–dependent mechanism, plant G proteins can function independently of nucleotide exchange.


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异源三聚体鸟嘌呤核苷酸结合蛋白G蛋白由α、β和γ三个亚基组成,是多功能的、鸟嘌呤核苷酸依赖型的分子开关。在动物和真菌中,α亚基上GDP到GTP的转变控制着G蛋白的活性,并且对于细胞对多种胞外信号的正常响应至关重要。在模式植物拟南芥中,只有一个经典的G蛋白α亚基,即AtGPA1。作者发现,在植物体内,组成型活跃的、能够结合GTP的AtGPA1(Q222L)突变体和不能结合核苷酸的AtGPA1(S52C)突变体都能够与Gβγ1和Gβγ2二聚体互作,并且亲和力并无明显差异,说明拟南芥中G蛋白异源三聚体的形成独立于核苷酸的交换。相反,AtGPA1(Q222L)突变体要比AtGPA1(S52C)突变体对于Gβγ3的亲和力更强,说明AtGPA1(Q222L)中结合GTP的特性与其能够与Gβγ3互作紧密关联。gpa1功能缺失突变体背景下AtGPA1(Q222L)和AtGPA1(S52C)的转基因株系功能分析显示gpa1突变体的各种缺陷表型都能够被AtGPA1(Q222L)或AtGPA1(S52C)所互补。因此,作者认为除了经典的GDP-GTP交换依赖型机制,植物的G-蛋白能够独立于核苷酸交换发挥功能。



通讯:Jose R. Botella (https://agriculture.uq.edu.au/profile/209/jimmy-botella)


个人简介:西班牙马德里大学,学士;西班牙马拉加大学,博士;密歇根州立大学、宾夕法尼亚州立大学,博士后。


研究方向:植物异三聚体G蛋白。



doi: 10.1126/scisignal.aav9526


Journal: Science Signaling

Published date: November 05, 2019


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http://blog.sciencenet.cn/blog-3158122-1210269.html

上一篇:Plant Cell:拟南芥维管组织发育的转录调控网络
下一篇:Nature Biotechnology:植物转基因新方法

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