Lenfant F, Labia R, Masson J M
INSA, Laboratoire de Génie Biochimique et Alimentaire, CNRS UA 544, Toulouse, France.
Biochimie. 1990 Jun-Jul;72(6-7):495-503. doi: 10.1016/0300-9084(90)90073-p.
Using a new extended set of 13 amber suppressors in E coli, systematic amino-acid replacements were performed at positions 104(E) and 238(G) of TEM-1 beta-lactamase from PUC19. The enzyme is tolerant to most substitutions tested at position 104. Missense revertants E104K, E104S or E104Y exhibited only minor changes in enzyme activity with respect to wild-type TEM-1. Several substitutions at position 238 resulted in a new cefotaxime hydrolysing capacity, but to an extent that did not confer cefotaxime resistance for the bacteria producing the mutated enzymes. Only when the mutations at codons 104 and 238 were combined on the same gene, did a true cefotaxime resistant phenotype appear, mimicking the situation encountered with 3rd generation cephalosporins resistant clinical isolates.
利用大肠杆菌中一组新的13种琥珀抑制子，对来自PUC19的TEM-1β-内酰胺酶的104位（E）和238位（G）进行了系统的氨基酸置换。该酶对在104位测试的大多数置换具有耐受性。错义回复突变体E104K、E104S或E104Y与野生型TEM-1相比，酶活性仅表现出微小变化。238位的几个置换导致了新的头孢噻肟水解能力，但程度不足以使产生突变酶的细菌对头孢噻肟产生抗性。只有当104位和238位的突变在同一基因上组合时，才会出现真正的头孢噻肟抗性表型，类似于耐第三代头孢菌素临床分离株的情况。
