Shaw J G, Hamblin M J, Kelly D J
Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, U.K.
Mol Microbiol. 1991 Dec;5(12):3055-62. doi: 10.1111/j.1365-2958.1991.tb01865.x.
A periplasmic binding protein essential for high-affinity transport of the C4-dicarboxylates malate, succinate and fumarate across the cytoplasmic membrane of the purple photosynthetic bacterium Rhodobacter capsulatus has been purified to homogeneity and some of its ligand-binding properties characterized. The protein was not produced in a Tn5 insertion mutant unable to transport C4-dicarboxylates under aerobic conditions in the dark. Wild-type DNA corresponding to the location of the transposon insertion site was subcloned and a 1.5 kb section sequenced. A complete open reading frame of 999 bp was identified that encoded a 333-residue protein (DctP) with a molecular weight of 36,128 with a 26-residue amino-terminal signal peptide. The identify of this protein with the purified dicarboxylate-binding protein and the position of the predicted signal peptide cleavage site was confirmed by N-terminal sequencing. No significant homology with other proteins was detected in database searches. A GC-rich region of dyad symmetry was located 7 bp downstream of the dctP translational stop codon. This structure may be of significance in regulating the relative abundance of DctP and other dct gene products which comprise the high-affinity dicarboxylate transport system in this bacterium.
一种对苹果酸、琥珀酸和富马酸等 C4-二羧酸跨紫色光合细菌荚膜红细菌细胞质膜进行高亲和力转运至关重要的周质结合蛋白已被纯化至同质，并对其一些配体结合特性进行了表征。在黑暗有氧条件下无法转运 C4-二羧酸的 Tn5 插入突变体中不产生该蛋白。与转座子插入位点位置相对应的野生型 DNA 被亚克隆，并对一个 1.5 kb 的片段进行了测序。鉴定出一个 999 bp 的完整开放阅读框，其编码一个 333 个氨基酸残基的蛋白质（DctP），分子量为 36,128，带有一个 26 个氨基酸残基的氨基末端信号肽。通过 N 端测序证实了该蛋白与纯化的二羧酸结合蛋白的一致性以及预测的信号肽切割位点的位置。在数据库搜索中未检测到与其他蛋白质的显著同源性。在 dctP 翻译终止密码子下游 7 bp 处定位到一个富含 GC 的二元对称区域。这种结构可能对调节 DctP 和构成该细菌高亲和力二羧酸转运系统的其他 dct 基因产物的相对丰度具有重要意义。
