Studies on the heme uptake system of a human pathogenic vibrio

创伤弧菌是一种能引起败血症或伤口感染的最佳人类病原体，它可以从多种血红素蛋白中获得铁。这一过程包括用外源蛋白酶消化血红素，使之脱除原血红素。在本研究中，我们研究了这种人致病弧菌的原血红素摄取系统。在许多人类病原体中，已知原血红素通过特定的外膜受体固定在细菌细胞表面。因此，我们最初测试了原血红素受体的存在。该细菌被发现在原血红素存在的情况下表达新的外膜蛋白。然而，这些蛋白中的任何一种都不能与原血红素结合，这表明创伤弧菌利用原血红素不依赖于外膜受体。我们分离并鉴定了一株利用原血红素的突变体。用化学诱变剂处理分离出的一个突变株被证明既不能使用原血红素蛋白，也不能使用血红素蛋白，但在添加铁铁载体的培养基中繁殖，如铁-vernibactin。这一发现表明创伤弧菌具有专门的原血红素摄取系统。3.创伤弧菌利用合成的血红素化合物(Fe-TPPs)和天然的化合物(原血红素)。利用任何一种血红素化合物的能力都被过量的铜-TPP竞争性地取消了，铜-TPP是一种类似于血红素的化合物。因此，创伤弧菌中的原血红素摄取系统可能不是特定的原血红素。

Vibrio vulnificus, an opprtunistic human pathogen causing septicemia or wound infection, can obtain iron from a variety of heme proteins. This process involves the digestion of heme proteins by an exoprotease to leberate protoheme. In the present study, we investigated the protoheme uptake system of this human pathogenic vibrio.1. In many human pathogens, protoheme is known to be fixed on the bacterial cell surface by the specific outer membrane receptor. Thus, we initially tested the presence of the protoheme receptor. The bacterium was found to express novel outer membrane proteins in the presence of protoheme. However, any of these proteins could not bind to protoheme, indicating V.vulnificus utilizes protoheme independent of the outer membrane receptor.2. We isolated and characterized a mutant for protoheme utilization. One mutant isolated by treatment with a chemical mutagen was shown to be unable to use either protoheme or heme proteins, but multiplied in a medium supplemented with an iron-siderophore, uch as iron-vulnibactin. This finding demonstrates that V.vulnificus has the specialized protoheme uptake system.3.V.vulnificus was found to utilize a synthetic heme compound (Fe-TPPS), as well as natural one(protoheme). The ability to utilize either heme compounds was competitively abolished by an excess amount of Cu-TPPS,an analog of the heme compound. Therefore, the protoheme uptake system in V.vulnificus may be not specific protoheme.