Nachin Laurence, Brive Lars, Persson Karin-Cecilia, Svensson Peder, Nyström Thomas
Department of Cell and Molecular Biology, Microbiology, Molecular Biology, Göteborg University, Box 462, 40530 Göteborg, Sweden.
J Mol Biol. 2008 Jul 4;380(2):340-50. doi: 10.1016/j.jmb.2008.04.074. Epub 2008 May 7.
Universal stress proteins (Usps) are found in all kingdoms of life and can be divided into four classes by phylogenic analysis. According to available structures, Usps exist as homodimers, and genetic studies show that their cellular assignments are extensive, including functions relating to stress resistance, carbon metabolism, cellular adhesion, motility, and bacterial virulence. We approached the question of how Usps can achieve such a variety of functions in a cell by using a new procedure for statistical analysis of multiple sequence alignments, based on physicochemically related values for each amino acid residue of Usp dimer interfaces. The results predicted that Usp proteins within a class may, in addition to forming homodimers, be able to form heterodimers. Using Escherichia coli Usps as model proteins, we confirmed the existence of such interactions. We especially focused on class I UspA and UspC and demonstrated that they are able to form homo- and heterodimers in vitro and in vivo. We suggest that this ability to form both homo- and heterodimers may allow for an expansion of the functional repertoire of Usps and explains why organisms usually contain multiple usp paralogues.
通用应激蛋白（Usps）存在于所有生物界，通过系统发育分析可分为四类。根据现有结构，Usps以同二聚体形式存在，遗传学研究表明它们在细胞中的作用广泛，包括与抗逆性、碳代谢、细胞黏附、运动性以及细菌毒力相关的功能。我们通过一种基于Usp二聚体界面每个氨基酸残基的物理化学相关值对多序列比对进行统计分析的新方法，探讨了Usps如何在细胞中实现如此多样的功能这一问题。结果预测，同一类中的Usp蛋白除了形成同二聚体外，还可能能够形成异二聚体。以大肠杆菌Usps作为模型蛋白，我们证实了这种相互作用的存在。我们特别关注I类UspA和UspC，并证明它们在体外和体内都能够形成同二聚体和异二聚体。我们认为，这种形成同二聚体和异二聚体的能力可能使Usps的功能库得以扩展，并解释了为什么生物体通常含有多个usp旁系同源物。
