Kwon Dong H, Versalovic James
Department of Biology, Long Island University, Brooklyn, New York 11201, USA.
Helicobacter. 2009 Apr;14(2):141-6. doi: 10.1111/j.1523-5378.2009.00669.x.
Helicobacter pylori infection is associated with a variety of diseases including gastric cancer. Flavodoxin is an electron transfer protein containing a flavin mononucleotide prosthetic group and substituted an iron-containing electron transfer protein under iron-limiting conditions. H. pylori flavodoxin has been reported but its pathogenic role is unclear. The aim of this study is to understand a pathogenic role of H. pylori flavodoxin under iron-limiting condition.
The flavodoxin-encoding gene (fldA) was cloned from one of clinical H. pylori isolates (DU17) and its transcript was quantified by primer extension, Northern hybridization, and real-time polymerase chain reaction in different concentrations of an iron chelator. The fldA transcript was also quantified in H. pylori ATCC 700392, lacking a ferric uptake regulatory (fur) protein.
Nucleotide sequence of the fldA from H. pylori DU17 revealed a 492-bp (164 amino acids) open reading frame with a deduced amino acid sequence having 97% identity to that from the complete genomic sequence of H. pylori 26695. The deduced promoter [-35, -10, and +1] of the fldA was 56-bp upstream from the first codon of FldA. The fldA transcript (approximately 0.55-kb) was induced up to 14-fold in both wild-type and fur-knocked-out strains under iron-limiting conditions, suggesting that the fldA induction is independent to the Fur protein.
The fldA gene may play an important role in iron starvation conditions.
幽门螺杆菌感染与包括胃癌在内的多种疾病相关。黄素氧还蛋白是一种含有黄素单核苷酸辅基的电子传递蛋白，在铁限制条件下可替代含铁电子传递蛋白。已有关于幽门螺杆菌黄素氧还蛋白的报道，但其致病作用尚不清楚。本研究旨在了解幽门螺杆菌黄素氧还蛋白在铁限制条件下的致病作用。
从一株临床幽门螺杆菌分离株（DU17）中克隆黄素氧还蛋白编码基因（fldA），并通过引物延伸、Northern杂交和实时聚合酶链反应在不同浓度的铁螯合剂中对其转录本进行定量。还在缺乏铁摄取调节（fur）蛋白的幽门螺杆菌ATCC 700392中对fldA转录本进行了定量。
幽门螺杆菌DU17的fldA核苷酸序列显示一个492 bp（164个氨基酸）的开放阅读框，推导的氨基酸序列与幽门螺杆菌266,95全基因组序列的氨基酸序列有97%的同一性。fldA推导的启动子[-35、-10和+1]位于FldA第一个密码子上游56 bp处。在铁限制条件下，野生型和fur基因敲除菌株中的fldA转录本（约0.55 kb）均诱导增加至14倍，提示fldA诱导与Fur蛋白无关。
fldA基因可能在铁饥饿条件下起重要作用。
