Department of Biochemistry, State University of New York, Buffalo, NY 14214, USA.
Proc Natl Acad Sci U S A. 2011 Sep 13;108(37):15390-5. doi: 10.1073/pnas.1110137108. Epub 2011 Aug 31.
The prevailing model of bacterial membrane function predicts that the outer membrane is permeable to most small solutes because of pores with limited selectivity based primarily on size. Here, we identified mnoP in the Gram-negative bacterium Bradyrhizobium japonicum as a gene coregulated with the inner membrane Mn(2+) transporter gene mntH. MnoP is an outer membrane protein expressed specifically under manganese limitation. MnoP acts as a channel to facilitate the tranlocation of Mn(2+), but not Co(2+) or Cu(2+), into reconstituted proteoliposomes. An mnoP mutant is defective in high-affinity Mn(2+) transport into cells and has a severe growth phenotype under manganese limitation. We suggest that the outer membrane is a barrier to divalent metal ions that requires a selective channel to meet the nutritional needs of the cell.
细菌膜功能的主流模型预测，由于基于大小的主要限制，外膜对大多数小分子溶质是可渗透的，因为有小孔，具有有限的选择性。在这里，我们鉴定出革兰氏阴性菌根瘤菌中的 mnoP 是与内膜 Mn(2+)转运蛋白基因 mntH 共同调控的基因。MnoP 是一种在锰限制下特异性表达的外膜蛋白。MnoP 作为一种通道，促进 Mn(2+)，而不是 Co(2+)或 Cu(2+)，易位到重组的蛋白脂质体中。mnoP 突变体在高亲和力 Mn(2+)向细胞内转运过程中存在缺陷，并且在锰限制下表现出严重的生长表型。我们认为，外膜是二价金属离子的屏障，需要一种选择性通道来满足细胞的营养需求。
