Neisseria meningitidis tonB, exbB, and exbD genes: Ton-dependent utilization of protein-bound iron in Neisseriae
Neisseria meningitidis tonB, exbB, and exbD genes: Ton-dependent utilization of protein-bound iron in Neisseriae
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DOI：
10.1128/jb.179.3.805-812.1997
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发表时间：
1997-02
影响因子：
3.2
通讯作者：
I. Stojiljković;N. Srinivasan
中科院分区：
文献类型：
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作者：
I. Stojiljković;N. Srinivasan
我们最近克隆了脑膜炎奈瑟氏菌血红蛋白（Hb）受体基因hmbR，并进行了表征。为了鉴定参与Hb利用的其他蛋白质，N.在大肠杆菌中重组脑膜炎球菌Hb利用系统。从N.脑膜炎球菌DNA文库使需要血红素（hemA）、表达HmbR的E.大肠杆菌以血红蛋白为卟啉和铁源。对从血红蛋白互补蛋白中亚克隆的DNA片段进行核苷酸序列分析，鉴定出4个开放阅读框，其中3个与恶臭假单胞菌、E.大肠杆菌和流感嗜血杆菌exbB、exbD和tonB基因。了N.脑膜炎球菌TonB蛋白与其它革兰氏阴性菌TonB蛋白的同源性为28.8%~ 33.6%，而脑膜炎球菌TonB蛋白与其它革兰氏阴性菌TonB蛋白的同源性为28.8%~ 33.6%。脑膜炎ExbD蛋白与其它ExbD和TolR蛋白共有23.3%至34.3%的相同氨基酸。了N.脑膜炎ExbB蛋白与其它革兰阴性菌ExbB和TolQ蛋白的同源性为24.7 ~ 36.1%。互补研究表明，奈瑟菌Ton系统不能与E. coli FhuA TonB依赖的外膜受体。了N. tonB突变体不能利用Hb、Hb-触珠蛋白复合物、转铁蛋白和乳铁蛋白作为铁源。在exbD基因的3'端插入抗生素盒产生渗漏表型。N.脑膜炎球菌tonB和exbD突变体表明存在一种非依赖于TON的血红素利用机制。E. coli互补研究和N. hmbR和hpu突变体提示在这种生物体中存在另一种Hb利用机制。
We have recently cloned and characterized the hemoglobin (Hb) receptor gene, hmbR, from Neisseria meningitidis. To identify additional proteins that are involved in Hb utilization, the N. meningitidis Hb utilization system was reconstituted in Escherichia coli. Five cosmids from N. meningitidis DNA library enabled a heme-requiring (hemA), HmbR-expressing mutant of E. coli to use Hb as both porphyrin and iron source. Nucleotide sequence analysis of DNA fragments subcloned from the Hb-complementing cosmids identified four open reading frames, three of them homologous to Pseudomonas putida, E. coli, and Haemophilus influenzae exbB, exbD, and tonB genes. The N. meningitidis TonB protein is 28.8 to 33.6% identical to other gram-negative TonB proteins, while the N. meningitidis ExbD protein shares between 23.3 and 34.3% identical amino acids with other ExbD and TolR proteins. The N. meningitidis ExbB protein was 24.7 to 36.1% homologous with other gram-negative ExbB and TolQ proteins. Complementation studies indicated that the neisserial Ton system cannot interact with the E. coli FhuA TonB-dependent outer membrane receptor. The N. meningitidis tonB mutant was unable to use Hb, Hb-haptoglobin complexes, transferrin, and lactoferrin as iron sources. Insertion of an antibiotic cassette in the 3' end of the exbD gene produced a leaky phenotype. Efficient usage of heme by N. meningitidis tonB and exbD mutants suggests the existence of a Ton-independent heme utilization mechanism. E. coli complementation studies and the analysis of N. meningitidis hmbR and hpu mutants suggested the existence of another Hb utilization mechanism in this organism.