Schneider R, Hantke K
Lehrstuhl für Mikrobiologie II, Universität Tübingen, Germany.
Mol Microbiol. 1993 Apr;8(1):111-21. doi: 10.1111/j.1365-2958.1993.tb01208.x.
Bacillus subtilis was shown to utilize three types of hydroxamate siderophores, ferrichromes, ferrioxamines and shizokinen, each of which is taken up by different transport systems. Mutants deficient in the uptake of ferrichrome and/or ferrioxamine B were isolated. The gene fhuD, which was able to complement a mutant defective in ferrichrome uptake, was cloned. The deduced sequence of FhuD showed low but significant homology to the binding proteins FepB, FecB and FhuD of Escherichia coli, which are all components of binding protein-dependent, ferric siderophore transport systems. The first 23 amino acids of FhuD of B. subtilis possessed all characteristics of a lipoprotein signal sequence. The processing of FhuD in E. coli was inhibited by globomycin. Inhibition by globomycin indicated a lipid modification at the N-terminal cysteine in E. coli. It is highly likely that this step may also take place in B. subtilis. As in other binding protein-dependent transport systems of Gram-positive organisms it is proposed that the lack of a periplasm is compensated for by the lipid through which the binding protein is anchored to the cytoplasmic membrane.
枯草芽孢杆菌被证明能利用三种类型的异羟肟酸铁载体，即铁色素、铁胺素和裂殖菌素，每一种都通过不同的转运系统被摄取。分离出了缺乏铁色素和/或铁胺素B摄取能力的突变体。克隆了能够互补铁色素摄取缺陷突变体的fhuD基因。FhuD推导的序列与大肠杆菌的结合蛋白FepB、FecB和FhuD显示出低但显著的同源性，这些蛋白都是依赖结合蛋白的铁载体转运系统的组成部分。枯草芽孢杆菌FhuD的前23个氨基酸具有脂蛋白信号序列的所有特征。FhuD在大肠杆菌中的加工受到球霉素的抑制。球霉素的抑制表明大肠杆菌中N端半胱氨酸发生了脂质修饰。很可能这一步骤在枯草芽孢杆菌中也会发生。正如在革兰氏阳性菌其他依赖结合蛋白的转运系统中一样，有人提出，缺乏周质可通过结合蛋白锚定在细胞质膜上的脂质来弥补。
