Bahrami Fariborz, Niven Donald F
Microbiology Unit, Department of Natural Resource Sciences, McGill University, Ste. Anne de Bellevue, Que., Canada H9X 3V9.
Microb Pathog. 2005 Jul-Aug;39(1-2):45-51. doi: 10.1016/j.micpath.2005.03.002.
Actinobacillus suis is an important swine pathogen. As with other pathogens, the ability of A. suis to acquire iron within the host is crucial for virulence. Here, we investigated the ability of seven strains of A. suis to acquire iron from haemoglobins. In growth assays, all strains could use porcine, bovine and human haemoglobins as iron sources for growth. Using solid phase binding assays, membranes derived from all strains, grown under iron-restricted conditions, were shown to bind all three haemoglobins. Competition binding assays indicated that these haemoglobins were bound by the same receptor and an affinity procedure allowed the isolation and identification of an iron-repressible, haemoglobin-binding polypeptide (approximately 105 kDa) from all strains. Nucleotide sequence analyses revealed that A. suis possesses a gene (hgbA) that encodes a homologue of the Actinobacillus pleuropneumoniae haemoglobin-binding protein, HgbA. hgbA, encoding a mature protein of 105 kDa, was shown to be preceded by a hugZ homologue; putative promoter sequences and a putative Fur box were located upstream of hugZ and RT-PCR revealed that hugZ and hgbA are co-transcribed and iron-repressible. It is concluded that the acquisition of haemoglobin-bound iron by A. suis involves a single-component receptor that is up-regulated in response to iron restriction.
猪放线杆菌是一种重要的猪病原体。与其他病原体一样，猪放线杆菌在宿主体内获取铁的能力对其毒力至关重要。在此，我们研究了七株猪放线杆菌从血红蛋白中获取铁的能力。在生长试验中，所有菌株都可以使用猪、牛和人血红蛋白作为生长的铁源。使用固相结合试验，在铁限制条件下生长的所有菌株的膜都显示能结合所有三种血红蛋白。竞争结合试验表明这些血红蛋白被相同的受体结合，并且一种亲和方法允许从所有菌株中分离和鉴定出一种铁可抑制的血红蛋白结合多肽（约105 kDa）。核苷酸序列分析表明猪放线杆菌拥有一个基因（hgbA），该基因编码胸膜肺炎放线杆菌血红蛋白结合蛋白HgbA的同源物。hgbA编码一个105 kDa的成熟蛋白，其前面有一个hugZ同源物；推测的启动子序列和一个推测的Fur框位于hugZ上游，逆转录-聚合酶链反应显示hugZ和hgbA是共转录的且受铁抑制。得出的结论是，猪放线杆菌获取血红蛋白结合铁涉及一种单组分受体，该受体在铁限制时上调。
