Functional analysis of glucan binding protein B from Streptococcus mutans
Functional analysis of glucan binding protein B from Streptococcus mutans
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DOI：
10.1128/jb.01845-05
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发表时间：
2006-06-01
影响因子：
3.2
通讯作者：
Duncan, Margaret J.
中科院分区：
文献类型：
--
作者：
Mattos-Graner, Renata O.;Porter, Kristen A.;Duncan, Margaret J.
变形链球菌是龋齿的主要病原体，其分泌的几种产物有助于细菌在牙齿上的积累。其中，变形链球菌葡聚糖结合蛋白B（Gbp B）是一种新的免疫优势蛋白。它的生物学功能尚不清楚，尽管GbpB与来自S. agalactiae和S. pneumoniae，表明在胞壁素生物合成中的作用。为了确定GbpB的细胞功能，我们使用了几种方法来克隆该基因，分析其表达，并鉴定相互作用的蛋白质。分析的转化体都不是真正的gbpB突变体，因为它们都含有破坏的和野生型基因拷贝，并且功能性GbpB的表达总是保守的。因此，无法获得可行的gbpB无效突变体支持gbpB是必需基因的观点。北方印迹和实时荧光PCR分析表明，诱导gbpB表达响应压力是一个应变依赖的现象。与GbpB相互作用的蛋白质在下拉和免疫共沉淀试验中被鉴定，这些数据表明GbpB与核糖体蛋白L7/L12相互作用，可能是参与肽聚糖合成和细胞分裂的蛋白质复合物的一部分。
Mutans streptococci are major etiological agents of dental caries, and several of their secreted products contribute to bacterial accumulation on teeth. Of these, Streptococcus mutans glucan binding protein B (GbpB) is a novel, immunologically dominant protein. Its biological function is unclear, although GbpB shares homology with a putative peptidoglycan hydrolase from S. agalactiae and S. pneumoniae, indicative of a role in murein biosynthesis. To determine the cellular function of GbpB, we used several approaches to inactivate the gene, analyze its expression, and identify interacting proteins. None of the transformants analyzed were true gbpB mutants, since they all contained both disrupted and wild-type gene copies, and expression of functional GbpB was always conserved. Thus, the inability to obtain viable gbpB null mutants supports the notion that gbpB is an essential gene. Northern blot and real-time PCR analyses suggested that induction of gbpB expression in response to stress was a strain-dependent phenomenon. Proteins that interacted with GbpB were identified in pull-down and coimmunoprecipitation assays, and these data suggest that GbpB interacts with ribosomal protein L7/L12, possibly as part of a protein complex involved in peptidoglycan synthesis and cell division.