Characterization of the gene family encoding alternative oxidase from Candida albicans
Characterization of the gene family encoding alternative oxidase from Candida albicans
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DOI：
10.1042/0264-6021:3560595
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发表时间：
2001-06-01
影响因子：
4.1
通讯作者：
Kang, SO
中科院分区：
文献类型：
--
作者：
Huh, WK;Kang, SO
白念珠菌具有由交替氧化酶(AOX)介导的抗氰化物呼吸途径，该途径似乎是由一个有两个成员的基因家族编码的。AOX1a是白念珠菌交替氧化酶的编码基因之一，已有报道[Huh，Kang(1999)J.细菌素]。181,4098-4102]。在本研究中，我们分离到了另一个编码交替氧化酶的基因，命名为AOX1b。AOX1b含有一个连续的开放阅读框架，编码365个氨基酸组成的多肽。有趣的是，AOX1a和AOX1b被发现位于白色念珠菌的一条染色体上。培养基中氰化物的存在显著抑制了aox1a/aox1a突变体的生长。在相同的培养条件下，aox1b/aox1b突变体和aox1a/aox1a aox1b/aox1b双突变体的生长几乎完全受到抑制。β-半乳糖苷酶报告基因分析表明，AOX1a是结构性表达的，而AOX1b的表达受氰化物、抗霉素A、H_2O_2、甲苯二酮和百草枯的诱导。细胞在含有不可发酵碳源的培养基中的生长也增强了AOX1b的表达。编码组氨酸激酶的CaSLN1似乎参与了白念珠菌AOX表达的调节，这是因为观察到在正常条件下，Casln1/Casln1突变株的抗氰呼吸活性和AOX的表达水平显著低于野生型菌株，而在呼吸抑制剂存在的情况下，AOX表达水平略有增加。和AOX1a一样，AOX1b也可以在AOX缺乏的酿酒酵母中进行功能表达，并赋予生物体抗氰化物呼吸。
Candida albicans possesses a cyanide-resistant respiratory pathway mediated by alternative oxidase (AOX), which seems to be encoded by a gene family with two members. Cloning and expression of AOX1a, one of the genes encoding alternative oxidase from C. albicans, has previously been reported [Huh and Kang (1999) J. Bacteriol. 181, 4098-4102]. In the present study we report the isolation of another gene coding for alternative oxidase, designated AOX1b. AOX1b contains a continuous open reading frame that encodes a polypeptide consisting of 365 amino acids. Interestingly, AOX1a and AOX1b were found to be located in tandem on one of the chromosomes of C. albicans. The presence of cyanide in the culture medium remarkably retarded the growth of the aox1a/aox1a mutants. The growth of the aox1b/aox1b mutants and the aox1a/aox1a aox1b/aox1b double mutants was almost completely inhibited in the same medium. beta -Galactosidase reporter assays indicated that, whereas AOX1a was expressed constitutively, the expression of AOX1b was dependent on growth phase and was induced by treatment with cyanide, antimycin A, H2O2, menadione and paraquat. Growth of the cells in media with non-fermentable carbon sources also enhanced the expression of AOX1b. CaSLN1, which encodes a histidine kinase, seems to be involved in the regulation of AOX expression in C. albicans on the basis of the observation that the activity of cyanide-resistant respiration and the expression level of AOX in the casln1/casln1 mutants were found to be significantly low under normal conditions and slightly increased in the presence of respiratory inhibitors compared with the wild-type strain. Like AOX1a, AOX1b could also be functionally expressed in AOX-deficient Saccharomyces cerevisiae and confer cyanide-resistant respiration on the organism.