Institute of Molecular Biology, Slovak Academy of Sciences, Dúbravská cesta 21, 84551 Bratislava, Slovakia.
Arch Microbiol. 2010 Mar;192(3):175-84. doi: 10.1007/s00203-009-0541-4.
Three complete katG genes coding for bifunctional catalase-peroxidases (KatGs) from the beta-proteobacterium Comamonas terrigena and two related strains of Comamonas testosteroni have been cloned and sequenced. Catalase-peroxidases are unique bifunctional enzymes known to be expressed in these soil bacteria in response to environmental and/or oxidative stress. The evolutionary and structural diversity of these enzymes is investigated based on multiple sequence alignment and comprehensive phylogenetic analysis. The reconstructed phylogenetic tree and well-known structure-function relationships were applied to inspect the conservation of essential residues. Observed diversity is discussed with respect to the fact that KatGs are distinctive gene-duplicated peroxidases comprising a N-terminal (enzymatically active) and a C-terminal (heme-less) domain. The unique promoter motifs regulating katG transcription in four strains of Comamonas were detected and compared with E. coli katG promoter. The relationship between the promoter sequences and the corresponding expression levels was analyzed. A significant difference in heat shock-inducible catalatic and peroxidatic activities between E. coli K12 and Comamonas terrigena & testosteroni strains was observed. The peculiar variability in gene-coding sequences appears to be more significant for such activity output among Comamonas strains than differences in their promoter regions. The functional role of observed increased diversity in the C-terminal domain is discussed with respect to potential modification of catalytic features at the N-terminal domain that could be relevant for these soil bacteria to cope with stressors.
The online version of this article (doi:10.1007/s00203-009-0541-4) contains supplementary material, which is available to authorized users.
从β变形菌恶臭假单胞菌和两个相关的睾丸酮假单胞菌菌株中克隆并测序了三个完整的编码双功能过氧化氢酶过氧化物酶（KatGs）的katG 基因。过氧化氢酶过氧化物酶是一种独特的双功能酶，已知在这些土壤细菌中表达，以应对环境和/或氧化应激。基于多序列比对和综合系统发育分析，研究了这些酶的进化和结构多样性。重建的系统发育树和众所周知的结构-功能关系被应用于检查必需残基的保守性。观察到的多样性与以下事实有关，即 KatGs 是独特的基因复制过氧化物酶，包含 N 端（酶活性）和 C 端（无血红素）结构域。在 4 株恶臭假单胞菌中检测到并比较了调节 katG 转录的独特启动子模体与大肠杆菌 katG 启动子。分析了启动子序列与相应表达水平之间的关系。观察到大肠杆菌 K12 和恶臭假单胞菌和睾丸酮假单胞菌菌株之间热休克诱导的过氧化氢酶和过氧化物酶活性存在显著差异。在基因编码序列中观察到的特殊可变性似乎对这些土壤细菌应对胁迫的活性输出比其启动子区域的差异更为重要。讨论了观察到的 C 端结构域增加多样性的功能作用，因为这可能对 N 端结构域的催化特征进行了潜在的修饰，这对于这些土壤细菌应对胁迫具有重要意义。
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