AB_5肠毒素A、B亚基比例表达调控机理的研究  

A New Model of Translational Control of Gene Expression in Polycistron of AB_5 Entrerotoxin

作　　者：曹诚[1] 李平[1] 王芃[1] 李杰之[1] 石成华[1] 马清钧[1] 

机构地区：[1]军事医学科学院生物工程研究所,北京100850

出　　处：《Acta Genetica Sinica》2000年第6期549-555,共7页

基　　金：北京市自然科学基金!5992014

摘　　要：霍乱毒素（CT）及大肠杆菌热不稳定肠毒素（LT）的B亚基基因的表达水平是A亚基的5～7倍。研究发现A基因内部存在着1个80bp长的翻译调控区，含有3个翻译起始序列（TIR），其第2个翻译起始序列的终止密码与第3个翻译起始序列的起始密码重叠，因而形成翻译偶联，继续翻译至A基因的终止密码。将TIR3的起始密码ATG突变为ATC后TIR2及TIR3失去功能，这时下游报告基因（类似于ctxB基因）表达水平降低9倍；为了更直接验证，去除了ctxA基因中与翻译起始调控及ctxA、B基因间翻译偶联调控所必须序列之外的其他序列，结果仍然表明TIR3的ATG突变为ACA后，下游基因表达水平降低9倍。结果表明：A亚基基因内部的翻译调控元件及翻译偶联是AB5素A、B亚基基因比例表达的原因。The expression level of the B subunit gene of cholera toxin (ctx) and Ecoli heat labile toxin (ltx) is five to seven times more than that of A subunit gene. Inthese studies, a 80 basepair translation regulation element was found located in thestructure gene of A gene of both toxin operon which consists of three translationinitiation region. Site-directed mutation of the initiation codon of TIR3 resulted in the9 time decrease of the expression of the downstream cistron which was translationalcoupled with A gene. The results indicated that translation from the internal of A geneand translation couping are responsile for the diferential expression level of the A andB gene of AB5 enterotoxin.

关 键 词：霍乱毒素 操纵子 翻译调控 基因表达 亚基 

分 类 号：Q756[生物学—分子生物学] Q342.4