Molecular characterization of HPr and related enzymes, and regulation of HPr phosphorylation in the ruminal bacterium Streptococcus bovis

被引:14
作者
Asanuma, N [1 ]
Hino, T [1 ]
机构
[1] Meijo Univ, Coll Agr, Dept Life Sci, Tama Ku, Kawasaki, Kanagawa 2148571, Japan
基金
日本学术振兴会;
关键词
ruminal bacterium; Streptococcus bovis; HPr; enzyme I; HPr kinase;
D O I
10.1007/s00203-003-0516-9
中图分类号
Q93 [微生物学];
学科分类号
071005 ; 100705 ;
摘要
Molecular properties of HPr, enzyme I, and HPr kinase in Streptococcus bovis, and the regulation of HPr phosphorylation were examined. The genes encoding HPr (ptsH) and enzyme I (ptsI) were found to be cotranscribed. Two transcriptional start sites were detected in a region upstream of the HPr kinase gene (hprK). HPr kinase had both HPr-phosphorylating and HPr-dephosphorylating activities. The importance of phosphorylation of Ser-46 in HPr was shown by using a mutant HPr in which Ser-46 was replaced by Ala. When S. bovis was grown in glucose-limited medium, the amount of seryl-phosphorylated HPr (HPr-[Ser-P]) decreased drastically as the growth rate decreased. In contrast, the amount of histidylphosphorylated HPr (HPr-[His-P]) increased gradually as the growth rate decreased. The amount of HPr kinase did not greatly change with the growth phase, whereas the intracellular P-i concentration increased as the growth rate decreased. HPr-[Ser-P] decreased as the intracellular P-i increased as a consequence of inhibition of HPr kinase activity by P-i and simultaneous enhancement of HPr-[Ser-P] phosphatase activity by P-i. Thus, it is conceivable that the ratio of HPr-[Ser-P] to HPr-[His-P] is regulated by the bifunctional activity of HPr kinase in response to intracellular P-i concentration.
引用
收藏
页码:205 / 213
页数:9
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