Lortie Louis-André, Pelletier Michel, Vadeboncoeur Christian, Frenette Michel
Groupe de Recherche en Ecologie Buccale, Département de Biochimie et de Microbiologie, Faculté des Sciences et de Génie, and Faculté de Médecine Dentaire, Université Laval, Québec, Canada G1K 7P41.
Microbiology (Reading). 2000 Mar;146 ( Pt 3):677-685. doi: 10.1099/00221287-146-3-677.
Glucose and mannose are transported in streptococci by the mannose-PTS (phosphoenolpyruvate:mannose phosphotransferase system), which consists of a cytoplasmic IIAB protein, called IIAB(Man), and an uncharacterized membrane permease. This paper reports the characterization of the man operon encoding the specific components of the mannose-PTS of Streptococcus salivarius. The man operon was composed of four genes, manL, manM, manN and manO. These genes were transcribed from a canonical promoter (Pman) into a 3.6 kb polycistronic mRNA that contained a 5'-UTR (untranslated region). The predicted manL gene product encoded a 35.5 kDa protein and contained the amino acid sequences of the IIA and IIB phosphorylation sites already determined from purified S. salivarius IIAB(Man)L. Expression of manL in Escherichia coli generated a 35 kDa protein that reacted with anti-IIAB(Man)L antibodies. The predicted ManM protein had an estimated size of 27.2 kDa. ManM had similarity with IIC domains of the mannose-EII family, but did not possess the signature proposed for mannose-IIC proteins from Gram-negative bacteria. From multiple alignment analyses of sequences available in current databases, the following modified IIC(Man) signature is proposed: GX3G[DNH]X3G[LIVM]2XG2[STL][LT][EQ]. The deduced product of manN was a hydrophobic protein with a predicted molecular mass of 33.4 kDa. The ManN protein contained an amino acid sequence similar to the signature sequence of the IID domains of the mannose-EII family. manO encoded a 13.7 kDa protein. This gene was also transcribed as a monocistronic mRNA from a promoter located in the manN-manO intergenic region. A search of current databases revealed the presence of IIAB(Man)L, ManM, ManN and ManO orthologues in Streptococcus mutans, Streptococcus pyogenes, Streptococcus pneumoniae and Enterococcus faecalis. This work has elucidated the molecular structure of the mannose PTS in streptococci and enterococci, and demonstrated the presence of a putative regulatory protein (ManO) within the man operon.
葡萄糖和甘露糖在链球菌中通过甘露糖磷酸烯醇丙酮酸磷酸转移酶系统（mannose-PTS）进行转运，该系统由一种细胞质IIAB蛋白（称为IIAB(Man)）和一种未鉴定的膜通透酶组成。本文报道了编码唾液链球菌甘露糖-PTS特定组分的man操纵子的特性。man操纵子由四个基因manL、manM、manN和manO组成。这些基因从一个典型启动子（Pman）转录成一个3.6 kb的多顺反子mRNA，该mRNA包含一个5'非翻译区（5'-UTR）。预测的manL基因产物编码一种35.5 kDa的蛋白质，并包含已从纯化的唾液链球菌IIAB(Man)L中确定的IIA和IIB磷酸化位点的氨基酸序列。manL在大肠杆菌中的表达产生了一种与抗IIAB(Man)L抗体反应的35 kDa蛋白质。预测的ManM蛋白估计大小为27.2 kDa。ManM与甘露糖-EII家族的IIC结构域相似，但不具有革兰氏阴性菌甘露糖-IIC蛋白所提出的特征序列。通过对当前数据库中可用序列的多序列比对分析，提出了以下修改后的IIC(Man)特征序列：GX³G[DNH]X³G[LIVM]²XG²[STL][LT][EQ]。推导的manN产物是一种疏水蛋白，预测分子量为33.4 kDa。ManN蛋白包含一个与甘露糖-EII家族IID结构域特征序列相似的氨基酸序列。manO编码一种13.7 kDa的蛋白质。该基因也从位于manN-manO基因间区域的一个启动子转录成单顺反子mRNA。对当前数据库的搜索揭示了变形链球菌、化脓性链球菌、肺炎链球菌和粪肠球菌中存在IIAB(Man)L、ManM、ManN和ManO的直系同源物。这项工作阐明了链球菌和肠球菌中甘露糖磷酸转移酶系统的分子结构，并证明了man操纵子内存在一种假定的调节蛋白（ManO）。
