兽疫链球菌磷脂酰甘油磷酸合成酶基因的分离

根据化脓链球菌(Streptococcus pyogenes)磷脂酰甘油磷酸合成酶（phosphatidylglycerophosphate synthase, PGPS）基因序列设计引物，通过PCR从兽疫链球菌（Streptococcus zooepidemicus）基因组中克隆得到开读框为531bp的同源序列pgsa-sz。pgsa-sz的预测编码蛋白含有176个氨基酸残基，分子量19400，等电点8.8，其中含有63个疏水氨基酸，预示其可能的膜结合特性。二级结构预测发现该蛋白含3个跨膜域。此外，该蛋白与S. pyogenes的PGPS具有85％的氨基酸序列相似性。将该蛋白与金黄色葡萄球菌(Staphylococcus aureus)、枯草芽孢杆菌(Bacillus subtilis)、大肠杆菌(Escherichia coli)和酿酒酵母(Saccharomyces cerevisiae)的PGPS进行序列比对，发现该蛋白包含PGPS中保守的活性位点区域。上述结果表明，pgsa-sz为S. zooepidemicus细胞膜中PGPS的编码基因。

Isolation of the gene encoding phosphatidylglycerophosphate synthase from S.zooepidemicus

The homologous sequence from Streptococcus zooepidemicus has been cloned by PCR using primers designed according to the pgsa gene encoding phosphatidylglycerophosphate synthase(PGPS) in Streptococcus pyogenes;it is designated as pgsa-sz.Its largest open reading frame was 531 bp in length and the putative protein(PGSA-SZ) comprised 176 acid residues.The presence of 63 hydrophobic amino acids in PGSA-SZ suggested a membrane-bound protein.In order to confirm this,SOPMA,TMHMM 2.0 programs and EMBOSS 4.0 software were employed to conduct hydrophobicity analysis and transmembrane prediction,and three transmembrane domains were found residing in the protein,which also appear in the PGPSs of other strains.PGSA-SZ not only shares 85% similarity with PGPS of S.pyogenes but,moreover,also retains its active site,which also exists in PGPSs of Spyogenes,Streptococcus aureus,Bacillus lichenifornis,Escherichia coli and Saccharomyces cerevisiae.The above evidence suggests that PGSA-SZ is the PGPS of S.zooepidemicus and is localized in the cytoplasmic membrane.