Broadbent J R, Oberg C J, Wei L
Utah State University, Department of Nutrition and Food Sciences, Logan 84322-8700, USA.
Res Microbiol. 1998 Apr;149(4):247-53. doi: 10.1016/s0923-2508(98)80300-8.
This study utilized inverse polymerase chain reactions to characterize a 2.7-kb region of the Lactobacillus helveticus LH212 chromosome that included two complete and one truncated open reading frames (ORFs). Protein homology searches showed that the first two ORFs encoded homologs to the universally conserved heat shock proteins GroES and GroEL. Amino acids encoded by the 5' end of the truncated ORF that was downstream of groEL showed good homology to the amino terminal end of the Streptococcus pneumoniae DNA mismatch repair enzyme HexA. Nucleotide sequence analysis identified a putative transcriptional promoter upstream of groES that was comprised of -35 and -10 hexamers flanked upstream and downstream by copies of the conserved Gram-positive heat shock gene regulatory sequence, CIRCE. A large inverted repeat that may function as a rho-independent transcriptional terminator was located between groEL and the third ORF. Northern hybridization of an LH212 groEL gene fragment to RNA isolated from cells that had been heat shocked at 52 degrees C for 0, 5, 10 or 15 min detected a 2.2-kb transcript in each of the cell preparations. Densitometry showed the concentration of this mRNA species was approximately 4-fold higher after heat shock for 5 or 10 min and 3-fold higher after 15 min of heat shock.
本研究利用反向聚合酶链反应来表征瑞士乳杆菌LH212染色体上一个2.7 kb的区域，该区域包含两个完整的开放阅读框（ORF）和一个截短的开放阅读框。蛋白质同源性搜索表明，前两个ORF编码与普遍保守的热休克蛋白GroES和GroEL同源的蛋白。位于groEL下游的截短ORF的5'端编码的氨基酸与肺炎链球菌DNA错配修复酶HexA的氨基末端具有良好的同源性。核苷酸序列分析在groES上游鉴定出一个假定的转录启动子，它由-35和-10六聚体组成，其上下游侧翼为保守的革兰氏阳性热休克基因调控序列CIRCE的拷贝。一个可能作为不依赖于ρ因子的转录终止子的大反向重复序列位于groEL和第三个ORF之间。用LH212 groEL基因片段与从在52℃热休克0、5、10或15分钟的细胞中分离的RNA进行Northern杂交，在每种细胞制备物中均检测到一个2.2 kb的转录本。光密度测定显示，热休克5或10分钟后，这种mRNA的浓度大约高4倍，热休克15分钟后高3倍。
