OmcF, a putative c-type monoheme outer membrane cytochrome required for the expression of other outer membrane cytochromes in Geobacter sulfurreducens
OmcF, a putative c-type monoheme outer membrane cytochrome required for the expression of other outer membrane cytochromes in Geobacter sulfurreducens
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DOI：
10.1128/jb.187.13.4505-4513.2005
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发表时间：
2005-07-01
影响因子：
3.2
通讯作者：
Lovley, DR
中科院分区：
文献类型：
--
作者：
Kim, BC;Leang, C;Lovley, DR
外膜细胞色素通常被认为是电子转移到细胞外电子受体（如Fe（III））的可能试剂。在异化Fe（III）-还原微生物Gesterylsulfurreducens中的omcF基因被预测编码一个小的外膜单血红素C型细胞色素。OmcF缺陷型菌株的构建，其能力，以减少和生长的Fe（III）柠檬酸盐被发现受损。经过一个长时间的滞后期（150小时），OmcF缺陷型菌株发展的能力，在铁（III）柠檬酸盐培养基中生长的倍增时间和产量约为。分别为野生型的145%和70%。从野生型和OmcF缺陷型培养物制备的外膜富集组分的c型细胞色素含量的比较证实了OmcF的外膜缔合，并揭示了OmcF缺陷型菌株的细胞色素含量的多种变化。这些变化包括两个先前表征的外膜细胞色素，OmcB和OmcC，和过度表达的第三个先前表征的外膜细胞色素，OmcS，在Fe（III）柠檬酸盐生长过程中的表达损失。通过逆转录PCR或北方印迹分析，在OmcF缺陷突变体中不能检测到omcB和omcC转录本。反式omcF基因的表达恢复了omcF缺陷突变体降低Fe（III）和野生型omcB和omcC mRNA和蛋白水平的能力。因此，OmcF的消除可能通过影响OmcB的表达而损害Fe（III）还原，OmcB先前已被证明在Fe（III）还原中起关键作用。
Outer membrane cytochromes are often proposed as likely agents for electron transfer to extracellular electron acceptors, such as Fe(III). The omcF gene in the dissimilatory Fe (III)-reducing microorganism Geobacter sulfurreducens is predicted to code for a small outer membrane monoheme c-type cytochrome. An OmcF-deficient strain was constructed, and its ability to reduce and grow on Fe(III) citrate was found to be impaired. Following a prolonged lag phase (150 h), the OmcF-deficient strain developed the ability to grow in Fe(III) citrate medium with doubling times and yields that were ca. 145% and 70% of those of the wild type, respectively. Comparison of the c-type cytochrome contents of outer membrane-enriched fractions prepared from wild-type and OmcF-deficient cultures confirmed the outer membrane association of OmcF and revealed multiple changes in the cytochrome content of the OmcF-deficient strain. These changes included loss of expression of two previously characterized outer membrane cytochromes, OmcB and OmcC, and overexpression of a third previously characterized outer membrane cytochrome, OmcS, during growth on Fe(III) citrate. The omcB and omcC transcripts could not be detected in the OmcF-deficient mutant by either reverse transcriptase PCR or Northern blot analyses. Expression of the omcF gene in trans restored both the capacity of the OmcF-deficient mutant to reduce Fe(III) and wild-type levels of omcB and omcC mRNA and protein. Thus, elimination of OmcF may impair Fe(III) reduction by influencing expression of OmcB, which has previously been demonstrated to play a critical role in Fe(III) reduction.