Martin-Verstraete I, Débarbouillé M, Klier A, Rapoport G
Unité de Biochimie Microbienne, Centre National de la Recherche Scientifique (URA 1300), Institut Pasteur, Paris, France.
J Mol Biol. 1990 Aug 5;214(3):657-71. doi: 10.1016/0022-2836(90)90284-S.
The levanase gene (sacC) of Bacillus subtilis is the distal gene of a fructose-inducible operon containing five genes. The complete nucleotide sequence of this operon was determined. The first four genes levD, levE, levF and levG encode polypeptides that are similar to proteins of the mannose phosphotransferase system of Escherichia coli. The levD and levE gene products are homologous to the N and C-terminal part of the enzyme IIIMan, respectively, whereas the levF and levG gene products have similarities with the enzymes IIMan. Surprisingly, the polypeptides encoded by the levD, levE, levF and levG genes are not involved in mannose uptake, but form a fructose phosphotransferase system in B. subtilis. This transport is dependent on the enzyme I of the phosphotransferase system (PTS) and is abolished by deletion of levF or levG and by mutations in either levD or levE. Four regulatory mutations (sacL) leading to constitutive expression of the lavanase operon were mapped using recombination experiments. Three of them were characterized at the molecular level and were located within levD and levE. The levD and levE gene products that form part of a fructose uptake PTS act as negative regulators of the operon. These two gene products may be involved in a PTS-mediated phosphorylation of a regulator, as in the bgl operon of E. coli.
枯草芽孢杆菌的果聚糖酶基因（sacC）是一个包含五个基因的果糖诱导型操纵子的远端基因。测定了该操纵子的完整核苷酸序列。前四个基因levD、levE、levF和levG编码的多肽与大肠杆菌甘露糖磷酸转移酶系统的蛋白质相似。levD和levE基因产物分别与酶IIIMan的N端和C端部分同源，而levF和levG基因产物与酶IIMan相似。令人惊讶的是，levD、levE、levF和levG基因编码的多肽不参与甘露糖摄取，而是在枯草芽孢杆菌中形成一个果糖磷酸转移酶系统。这种转运依赖于磷酸转移酶系统（PTS）的酶I，并且通过缺失levF或levG以及levD或levE中的突变而被消除。使用重组实验定位了导致果聚糖酶操纵子组成型表达的四个调控突变（sacL）。其中三个在分子水平上进行了表征，并且位于levD和levE内。构成果糖摄取PTS一部分的levD和levE基因产物作为操纵子的负调控因子。这两种基因产物可能参与了PTS介导的调控因子磷酸化，如大肠杆菌的bgl操纵子。
