Nielsen A K, Gerdes K, Murrell J C
Department of Molecular Biology, Odense University, Odense M, Denmark.
Mol Microbiol. 1997 Jul;25(2):399-409. doi: 10.1046/j.1365-2958.1997.4801846.x.
The methanotrophic bacteria Methylococcus capsulatus (Bath) and Methylosinus trichosporium OB3b convert methane to methanol using the enzyme, methane monooxygenase (MMO). These bacteria are able to express two distinct MMOs: a cytoplasmic or soluble form (sMMO) and a membrane-bound or particulate form (pMMO). Differential expression of sMMO and pMMO is regulated by the amount of copper ions available to the cells; sMMO is expressed at low copper-biomass ratios, whereas pMMO is expressed at high copper-biomass ratios. In both methanotrophs, transcription of the sMMO gene cluster is negatively regulated by copper ions. Data suggest that transcription of the M. trichosporium OB3b sMMO gene cluster is directed from a sigma54-like and a sigma70-like promoter. The pMMO (pmo) genes of M. capsulatus (Bath) are transcribed into a polycistronic mRNA of 3.3 kb. The synthesis of this mRNA was activated by copper ions. Activation of pmo transcription by copper ions was concomitant with repression of sMMO gene transcription in both methanotrophs. This suggests that a common regulatory pathway may be involved in the transcriptional switch between sMMO and pMMO gene expression.
甲烷氧化菌荚膜甲基球菌(巴斯)和嗜甲基丝孢菌OB3b利用甲烷单加氧酶(MMO)将甲烷转化为甲醇。这些细菌能够表达两种不同的MMO:一种是胞质或可溶性形式(sMMO),另一种是膜结合或颗粒形式(pMMO)。sMMO和pMMO的差异表达受细胞可利用的铜离子量的调节;sMMO在低铜生物量比时表达,而pMMO在高铜生物量比时表达。在这两种甲烷氧化菌中,sMMO基因簇的转录均受铜离子的负调控。数据表明,嗜甲基丝孢菌OB3b的sMMO基因簇转录由一个类σ54启动子和一个类σ70启动子指导。荚膜甲基球菌(巴斯)的pMMO(pmo)基因转录成一个3.3 kb的多顺反子mRNA。该mRNA的合成受铜离子激活。在这两种甲烷氧化菌中,铜离子对pmo转录的激活与sMMO基因转录的抑制同时发生。这表明sMMO和pMMO基因表达之间的转录转换可能涉及一条共同的调控途径。