Genetic and biochemical properties of streptococcal NAD-glycohydrolase inhibitor
Genetic and biochemical properties of streptococcal NAD-glycohydrolase inhibitor
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DOI：
10.1074/jbc.m506879200
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发表时间：
2006-04-07
影响因子：
4.8
通讯作者：
Taketo, A
中科院分区：
文献类型：
--
作者：
Kimoto, H;Fujii, Y;Taketo, A
编码溶血性链球菌的溶细胞素的链球菌溶血素O（Streptolysin O，NGA）的基因从前面的NAD-糖水解酶（NAD ase）基因（nga）的启动子多顺反子转录。在nga和nga之间，存在一个假定的开放阅读框架（orf 1），其功能完全未知。目前的研究表明，orf 1编码的蛋白命名为链球菌NAD酶抑制剂（SNI）。从其核苷酸序列推断，SNI由161个氨基酸残基组成，推测分子量为18，800。这种蛋白质仅在细胞内可检测到。在重组大肠杆菌中，SNI的共表达是产生链球菌NAD酶的必要条件，而NAD酶前体与SNI以无活性的复合物形式存在。单体NADase和SNI在体外以1：1的比例迅速形成稳定的异源二聚体复合物，导致水解酶活性的完全抑制。与其他细菌NAD酶抑制剂不同，SNI是热稳定的。该蛋白与NAD酶共表达并复合，可保护生产球菌免于NAD耗尽。
The gene encoding streptolysin O (slo), a cytolysin of hemolytic streptococci, is transcribed polycistronically from the promoter of the preceding NAD-glycohydrolase (NADase) gene (nga). Between nga and slo, a putative open reading frame (orf1) is located whose function has been totally unknown. Present investigation demonstrated that the orf1 encodes a protein designated as streptococcal NADase inhibitor (SNI). From its nucleotide sequence, SNI was inferred to comprise 161 amino acid residues and the deduced molecular weight was 18,800. This protein was detectable only within cells. Coexpression of SNI was essential for production of streptococcal NADase, and NADase precursor existed as an inactive complex with SNI, in recombinant Escherichia coli. Monomeric NADase and SNI rapidly formed in vitro a stable heterodimer complex in the ratio 1:1, resulting in complete suppression of the hydrolase activity. Unlike other bacterial NADase inhibitors, SNI was thermostable. This protein, coexpressed and complexed with NADase, may protect the producer cocci from exhaustion of NAD.