Vickerman M M, Mather N M, Minick P E, Edwards C A
Department of Oral Surgery and Hospital Dentistry, School of Dentistry, Indiana University, 1121 West Michigan Street, Indianapolis, IN 46202, USA.
Oral Microbiol Immunol. 2002 Feb;17(1):22-31. doi: 10.1046/j.0902-0055.2001.00000.x.
Examination of the Streptococcus gordonii chromosomal region, which lies immediately upstream of the glucosyltransferase positive regulatory determinant rgg, revealed two open reading frames. Based on nucleotide sequences, these genes were similar to the Listeria monocytogenes lemA gene, which is involved in antigen presentation, and the Escherichia coli htpX heat shock gene, which has an unknown function. Northern hybridization analysis indicated that S. gordonii lemA and htpX genes were associated with a ca. 1.7-kb polycistronic transcript. Although levels of the lemA/htpX transcript did not increase in response to heat to levels seen with dnaK controls, insertional inactivation of htpX resulted in changes in adhesiveness, cellular morphology and detergent-extractable surface antigens in cells grown at 41 degrees C, implying that htpX may be involved in surface protein expression. Insertional inactivation of lemA and htpX indicated that, despite their proximity to rgg and the structural gene, gtfG, these upstream genes do not affect S. gordonii glucosyltransferase activity.
对戈登氏链球菌染色体区域（该区域紧邻葡糖基转移酶阳性调节决定簇rgg的上游）进行检测，发现了两个开放阅读框。根据核苷酸序列，这些基因与单核细胞增生李斯特菌中参与抗原呈递的lemA基因以及功能未知的大肠杆菌htpX热休克基因相似。Northern杂交分析表明，戈登氏链球菌lemA和htpX基因与一个约1.7 kb的多顺反子转录本相关。尽管lemA/htpX转录本的水平不会因热刺激而升高至与dnaK对照相同的水平，但htpX的插入失活导致在41摄氏度下生长的细胞的黏附性、细胞形态和可被去污剂提取的表面抗原发生变化，这意味着htpX可能参与表面蛋白的表达。lemA和htpX的插入失活表明，尽管它们与rgg和结构基因gtfG相邻，但这些上游基因并不影响戈登氏链球菌的葡糖基转移酶活性。
