流产布氏杆菌烯脂酰ACP还原酶的鉴定

烯脂酰ACP还原酶是细菌脂肪酸合成的关键酶之一．流产布氏杆菌基因组有2个注释为烯脂酰ACP还原酶基因fabI的同源基因：fabI1和fabI2．由这2个fabI同源基因编码的蛋白质分别与大肠杆菌FabI有50%和51%的同源性，且都拥有与大肠杆菌FabI一样的催化中心Tyr-(Xaa)₆-Lys序列．分别用携带这2个同源基因的质粒载体转化大肠杆菌fabI温度敏感突变菌株JP1111．转化子能在42℃生长，表明这2个基因均能遗传互补大肠杆菌fabI突变，并使此菌株恢复脂肪酸的合成．另外，体外酶学分析显示，由这2个同源基因编码的蛋白质都拥有烯脂酰ACP还原酶活性，均能参与细菌脂肪酸合成．上述结果证实，流产布氏杆菌同时拥有2个同种类型的烯脂酰ACP还原酶，是一种新的烯脂酰ACP多样性的表现．

Identification of Two Enoyl-ACP Reductase FabI1 and FabI2 in Brucella abortus

There are two genes, fabI1 and fabI2 (UniProt AC: Q57A95 and Q57EU5), annotated as encodes putative enoyl-ACP reductase in Brucella abortus genome. Sequence alignment found that BaFabI1 and BaFabI2 are 50% and 51% identical to E. coli FabI, respectively. Further analysis identified that the catalytically active triad (Tyr-(Xaa)₆-Lys) of E. coli FabI are present in both BaFabI1 and BaFabI2. Expression of either of the two proteins restores the growth and the fatty acid synthesis of the E. coli fabI temperature sensitive mutant JP1111 under nonpermissive condition. In vitro assay identifies that both proteins restore the fatty acid synthetic ability and are active with substrates of all fatty acid chain lengths. These results demonstrated that B. abortus possesses two FabI-like enoyl-ACP reductases and it represents a new kind of diversity of bacterial enoyl-ACP reductase.