Beloin C, Ayora S, Exley R, Hirschbein L, Ogasawara N, Kasahara Y, Alonso J C, Hégarat F L
Institut de Génétique et Microbiologie, Université Paris XI, Orsay, France.
Mol Gen Genet. 1997 Sep;256(1):63-71. doi: 10.1007/s004380050546.
In the course of the Bacillus subtilis genome sequencing project, we identified an open reading frame encoding a putative 16.4 kDa protein. This protein shows, respectively, 34% and 25% identity with the Escherichia coli regulatory proteins Lrp and AsnC. Phylogenetic analysis suggests that it represents a new group in the AsnC-Lrp family. Sequence comparisons, as well as immunodetection experiments, lead to the conclusion that the product of this B. subtilis lrp-like-gene is a bona fide Lrp protein-the first one to be detected in gram-positive bacteria. When expressed in E. coli, the B. subtilis Lrp-like protein is able to repress, by about two-fold, the expression of the ilvIH operon which is normally regulated by E. coli Lrp, indicating functional similarity in their regulatory targets. Vegetative growth of a B. subtilis lrp-like mutant is not affected in rich medium. However, the lrp-like mutation causes a transitory inhibition of growth in minimal medium in the presence of valine and isoleucine, which is relieved by leucine. This points to a possible role in regulation of amino acid metabolism. In addition, sporogenesis occurs earlier in the lrp-like mutant than in the reference strain, implying that the B subtilis Lrp-like protein plays a role in the growth phase transition.
在枯草芽孢杆菌基因组测序项目过程中，我们鉴定出一个编码假定的16.4 kDa蛋白的开放阅读框。该蛋白分别与大肠杆菌调节蛋白Lrp和AsnC具有34%和25%的同一性。系统发育分析表明，它代表AsnC-Lrp家族中的一个新组。序列比较以及免疫检测实验得出结论，该枯草芽孢杆菌类lrp基因的产物是一种真正的Lrp蛋白——这是在革兰氏阳性细菌中首次检测到的此类蛋白。当在大肠杆菌中表达时，枯草芽孢杆菌类Lrp蛋白能够将ilvIH操纵子的表达抑制约两倍，该操纵子通常由大肠杆菌Lrp调节，这表明它们在调节靶点上具有功能相似性。枯草芽孢杆菌类lrp突变体的营养生长在丰富培养基中不受影响。然而，类lrp突变在存在缬氨酸和异亮氨酸的基本培养基中会导致生长的短暂抑制，而亮氨酸可缓解这种抑制。这表明其在氨基酸代谢调节中可能发挥作用。此外，类lrp突变体中的孢子形成比参考菌株更早发生，这意味着枯草芽孢杆菌类Lrp蛋白在生长阶段转变中发挥作用。
