Balan Andrea, Santacruz-Pérez Carolina, Moutran Alexandre, Ferreira Luís Carlos Souza, Neshich Goran, Gonçalves Barbosa João Alexandre Ribeiro
Departamento de Microbiologia, Instituto de Ciências Biomédicas II, Universidade de São Paulo, Cidade Universitária, São Paulo, SP, 05008-900, Brazil.
Biochim Biophys Acta. 2008 Feb;1784(2):393-9. doi: 10.1016/j.bbapap.2007.11.013. Epub 2007 Nov 29.
In Xanthomonas axonopodis pv. citri (Xac or X. citri), the modA gene codes for a periplasmic protein (ModA) that is capable of binding molybdate and tungstate as part of the ABC-type transporter required for the uptake of micronutrients. In this study, we report the crystallographic structure of the Xac ModA protein with bound molybdate. The Xac ModA structure is similar to orthologs with known three-dimensional structures and consists of two nearly symmetrical domains separated by a hinge region where the oxyanion-binding site lies. Phylogenetic analysis of different ModA orthologs based on sequence alignments revealed three groups of molybdate-binding proteins: bacterial phytopathogens, enterobacteria and soil bacteria. Even though the ModA orthologs are segregated into different groups, the ligand-binding hydrogen bonds are mostly conserved, except for Archaeglobus fulgidus ModA. A detailed discussion of hydrophobic interactions in the active site is presented and two new residues, Ala38 and Ser151, are shown to be part of the ligand-binding pocket.
在柑桔溃疡病菌（Xanthomonas axonopodis pv. citri，简称Xac或X. citri）中，modA基因编码一种周质蛋白（ModA），作为摄取微量营养素所需的ABC型转运蛋白的一部分，该蛋白能够结合钼酸盐和钨酸盐。在本研究中，我们报道了结合钼酸盐的Xac ModA蛋白的晶体结构。Xac ModA结构与具有已知三维结构的直系同源物相似，由两个近乎对称的结构域组成，中间由一个铰链区隔开，氧阴离子结合位点位于该区域。基于序列比对的不同ModA直系同源物的系统发育分析揭示了三类钼酸盐结合蛋白：细菌性植物病原体、肠杆菌和土壤细菌。尽管ModA直系同源物被分为不同的组，但除了嗜热栖热菌ModA外，配体结合氢键大多是保守的。本文详细讨论了活性位点中的疏水相互作用，并表明两个新的残基Ala38和Ser151是配体结合口袋的一部分。
