Distinctive properties of Arabidopsis SUMO paralogues support the in vivo predominant role of AtSUMO1/2 isoforms.
Distinctive properties of Arabidopsis SUMO paralogues support the in vivo predominant role of AtSUMO1/2 isoforms.
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DOI：
10.1042/bj20101446
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发表时间：
2011-06-15
期刊：
影响因子：
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通讯作者：
Lois LM
中科院分区：
文献类型：
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作者：
Castaño-Miquel L;Seguí J;Lois LM
SUMO（small ubiquitin-related modifier）修饰蛋白质已成为真核生物中一种重要的调控机制。尽管SUMO结合/去结合的分子机制是保守的，但SUMO机制组件的数量及其保守程度对每个生物体都是特定的。在本论文中，我们显示的数据有助于这一概念，即四个表达的拟南芥SUMO旁系同源物，AtSUMO 1，2，3和5，功能分歧的程度高于他们的人类直系同源物。我们已经探索了这些旁系同源物的保守程度，发现参与E1-激活酶识别，E2-缀合酶和SIM（SUMO相互作用基序）的非共价相互作用的表面在AtSUMO 1/2亚型中是很保守的，而AtSUMO 3显示出较低的保守程度，AtSUMO 5是最不同的亚型。这些差异是功能相关的，因为AtSUMO 3和5在建立E2非共价相互作用方面存在缺陷，这对于任何天然存在的SUMO直向同源物都没有报道。此外，AtSUMO 3的缀合效率低于AtSUMO 1/2，AtSUMO 5显示最低的缀合水平。诱变分析表明，共轭率和硫酯键形成的减少是参与E1激活酶识别的非保守残基的结果，这些残基存在于AtSUMO 3和5中。本研究的结果支持E1激活酶在SUMO旁系同源物识别中的作用，提供了一种新的机制，有利于必要的AtSUMO 1/2旁系同源物的结合。
Protein modification by SUMO (small ubiquitin-related modifier) has emerged as an essential regulatory mechanism in eukaryotes. Even though the molecular mechanisms of SUMO conjugation/deconjugation are conserved, the number of SUMO machinery components and their degree of conservation are specific to each organism. In the present paper, we show data contributing to the notion that the four expressed Arabidopsis SUMO paralogues, AtSUMO1, 2, 3 and 5, have functionally diverged to a higher extent than their human orthologues. We have explored the degree of conservation of these paralogues and found that the surfaces involved in E1-activating enzyme recognition, and E2-conjugating enzyme and SIM (SUMO-interacting motif) non-covalent interactions are well conserved in AtSUMO1/2 isoforms, whereas AtSUMO3 shows a lower degree of conservation, and AtSUMO5 is the most divergent isoform. These differences are functionally relevant, since AtSUMO3 and 5 are deficient in establishing E2 non-covalent interactions, which has not been reported for any naturally occurring SUMO orthologue. In addition, AtSUMO3 is less efficiently conjugated than AtSUMO1/2, and AtSUMO5 shows the lowest conjugation level. A mutagenesis analysis revealed that decreases in conjugation rate and thioester-bond formation are the result of the non-conserved residues involved in E1-activating enzyme recognition that are present in AtSUMO3 and 5. The results of the present study support a role for the E1-activating enzyme in SUMO paralogue discrimination, providing a new mechanism to favour conjugation of the essential AtSUMO1/2 paralogues.