Doran J L, Pang Y, Mdluli K E, Moran A J, Victor T C, Stokes R W, Mahenthiralingam E, Kreiswirth B N, Butt J L, Baron G S, Treit J D, Kerr V J, Van Helden P D, Roberts M C, Nano F E
Department of Biochemistry and Microbiology, University of Victoria, British Columbia, Canada.
Clin Diagn Lab Immunol. 1997 Jan;4(1):23-32. doi: 10.1128/cdli.4.1.23-32.1997.
The Mycobacterium tuberculosis H37Rv efpA gene encodes a putative efflux protein, EfpA, of 55,670 Da. The deduced EfpA protein was similar in secondary structure to Pur8, MmrA, TcmA, LfrA, EmrB, and other members of the QacA transporter family (QacA TF) which mediate antibiotic and chemical resistance in bacteria and yeast. The predicted EfpA sequence possessed all transporter motifs characteristic of the QacA TF, including those associated with proton-antiport function and the motif considered to be specific to exporters. The 1,590-bp efpA open reading frame was G+C rich (65%), whereas the 40-bp region immediately upstream had an A+T bias (35% G+C). Reverse transcriptase-PCR assays indicated that efpA was expressed in vitro and in situ. Putative promoter sequences were partially overlapped by the A+T-rich region and by a region capable of forming alternative secondary structures indicative of transcriptional regulation in analogous systems. PCR single-stranded conformational polymorphism analysis demonstrated that these upstream flanking sequences and the 231-bp, 5' coding region are highly conserved among both drug-sensitive and multiply-drug-resistant isolates of M. tuberculosis. The efpA gene was present in the slow-growing human pathogens M. tuberculosis, Mycobacterium leprae, and Mycobacterium bovis and in the opportunistic human pathogens Mycobacterium avium and Mycobacterium intracellular. However, efpA was not present in 17 other opportunistically pathogenic or nonpathogenic mycobacterial species.
结核分枝杆菌H37Rv的efpA基因编码一种推定的外排蛋白EfpA，分子量为55,670道尔顿。推导的EfpA蛋白二级结构与Pur8、MmrA、TcmA、LfrA、EmrB以及QacA转运蛋白家族（QacA TF）的其他成员相似，这些成员介导细菌和酵母中的抗生素及化学抗性。预测的EfpA序列具有QacA TF所有典型的转运基序，包括那些与质子反向转运功能相关的基序以及被认为是输出蛋白特有的基序。1590 bp的efpA开放阅读框富含G+C（65%），而紧邻的上游40 bp区域则具有A+T偏向性（35% G+C）。逆转录酶PCR分析表明efpA在体外和体内均有表达。推定的启动子序列部分与富含A+T的区域以及一个能够形成指示类似系统转录调控的替代二级结构的区域重叠。PCR单链构象多态性分析表明，这些上游侧翼序列以及231 bp的5'编码区域在结核分枝杆菌的药物敏感株和多重耐药株中高度保守。efpA基因存在于生长缓慢的人类病原体结核分枝杆菌、麻风分枝杆菌和牛分枝杆菌以及机会性人类病原体鸟分枝杆菌和胞内分枝杆菌中。然而，efpA在其他17种机会性致病或非致病分枝杆菌物种中不存在。
