Porphyromonas gingivalis HmuY and HmuR:: further characterization of a novel mechanism of heme utilization
Porphyromonas gingivalis HmuY and HmuR:: further characterization of a novel mechanism of heme utilization
复制标题
DOI：
10.1007/s00203-007-0309-7
复制
发表时间：
2008-03-01
影响因子：
2.8
通讯作者：
Olczak, Mariusz
中科院分区：
文献类型：
--
作者：
Olczak, Teresa;Sroka, Aneta;Olczak, Mariusz
牙龈卟啉单胞菌HmuY是一种推定的血红素结合脂蛋白与外膜。它是操纵子的一部分，与编码外膜氯化血红素利用受体（HmuR）的基因和四个未表征的基因一起。在脆弱拟杆菌和B中发现了类似的操纵子结构。多形核，前者含有在hmuR样基因上游编码的额外的HmuY同源物。在血红素限制条件下培养的牙龈卟啉单胞菌中，沿着高水平产生类似于1-kb的hmuY转录物以及一些类似于3.5和类似于9-kb的转录物。与亲本菌株相比，hmuY或hmuR或hmuY-hmuR基因功能缺陷的突变体生长更慢，结合的氯化血红素和血红蛋白的量更低。值得注意的是，当使用人血清作为唯一的铁/血红素来源时，它们生长得更慢或无法生长。对hmu启动子的分析表明它受铁的调控。HmuY蛋白通常以同源二聚体形式存在，但在氯化血红素存在下，它可以形成四聚体。这些结果表明，HmuY可能是第一个报告的成员的一类新的蛋白质在卟啉单胞菌和拟杆菌物种参与血红素利用，发挥功能与HmuR，外膜血红素转运蛋白。
Porphyromonas gingivalis HmuY is a putative heme-binding lipoprotein associated with the outer membrane. It is part of an operon together with a gene encoding an outer-membrane hemin utilization receptor (HmuR) and four uncharacterized genes. A similar operon organization was found in Bacteroides fragilis and B. thetaiotaomicron, with the former containing an additional HmuY homologue encoded upstream of the hmuR-like gene. In P. gingivalis cultured under heme-limited conditions, similar to 1-kb hmuY transcript was produced at high levels along with some similar to 3.5 and similar to 9-kb transcripts. Compared with the parental strain, mutants deficient in hmuY or hmuR or hmuY-hmuR gene function grew more slowly and bound lower amounts of hemin and hemoglobin. Significantly, they grew more slowly or were unable to grow when human serum was used as the sole iron/heme source. Analysis of the hmu promoter showed that it is regulated by iron. The HmuY protein normally occurs as a homodimer, but in the presence of hemin it may form tetramers. These results show that HmuY may be the first reported member of a new class of proteins in Porphyromonas and Bacteroides species involved in heme utilization, a function being exerted in conjunction with HmuR, an outer-membrane heme transporter.