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首页> 外文期刊>Journal of bacteriology >Transcriptional analysis of pqqD and study of the regulation of pyrroloquinoline quinone biosynthesis in Methylobacterium extorquens AM1.
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Transcriptional analysis of pqqD and study of the regulation of pyrroloquinoline quinone biosynthesis in Methylobacterium extorquens AM1.

机译：pqqD的转录分析和吡咯喹啉AM1吡咯并喹啉醌生物合成调控的研究。

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Methanol dehydrogenase, the enzyme that oxidizes methanol to formaldehyde in gram-negative methylotrophs, contains the prosthetic group pyrroloquinoline quinone (PQQ). To begin to analyze how the synthesis of PQQ is coordinated with the production of other methanol dehydrogenase components, the transcription of one of the key PQQ synthesis genes has been studied. This gene (pqqD) encodes a 29-amino-acid peptide that is thought to be the precursor for PQQ biosynthesis. A unique transcription start site was mapped to a guanidine nucleotide 95 bp upstream of the pqqD initiator codon. RNA blot analysis identified two transcripts, a major one of 240 bases encoding pqqD and a minor one of 1,300 bases encoding pqqD and the gene immediately downstream, pqqG. Both transcripts are present at similar levels in cells grown on methanol and on succinate, but the levels of PQQ are about fivefold higher in cells grown on methanol than in cells grown on succinate. These results suggest that PQQ production is regulated at a level different from the transcription of pqqD. The genes mxbM, mxbD, mxcQ, mxcE, and mxaB are required for transcription of the genes encoding the methanol dehydrogenase subunits and were assessed for their role in PQQ production. PQQ levels were measured in mutants defective in each of these regulatory genes and compared with levels of pqqD transcription, measured with a transcriptional fusion between the pqqD promoter and xylE. The results showed that only a subset of these regulatory genes (mxbM, mxbD, and mxaB) is required for transcription of pqqD, and only mxbM and mxbD mutants affected the final levels of PQQ significantly.
机译：甲醇脱氢酶是革兰氏阴性甲基营养菌中将甲醇氧化为甲醛的酶，其中含有辅基吡咯并喹啉醌（PQQ）。为了开始分析PQQ的合成与其他甲醇脱氢酶成分的生产如何协调，已经研究了关键PQQ合成基因之一的转录。该基因（pqqD）编码一个29个氨基酸的肽，被认为是PQQ生物合成的前体。独特的转录起始位点被映射到pqqD起始密码子上游95 bp的胍核苷酸。 RNA印迹分析确定了两个转录本，一个主要的编码pqqD的240个碱基中的一个，另一个是一个编码pqqD的1300个碱基中的一个，以及紧接下游的基因pqqG。两种转录物在甲醇和琥珀酸盐上生长的细胞中存在的水平相似，但在甲醇中生长的细胞中PQQ的水平比在琥珀酸盐中生长的细胞高约五倍。这些结果表明，PQQ产生的调控水平与pqqD的转录不同。编码甲醇脱氢酶亚基的基因转录需要基因mxbM，mxbD，mxcQ，mxcE和mxaB，并评估了它们在PQQ生产中的作用。在每个调节基因中有缺陷的突变体中测量PQQ水平，并将其与pqqD转录水平进行比较，而pqqD转录水平则通过pqqD启动子和xylE之间的转录融合来测量。结果表明，pqqD的转录仅需要这些调节基因的一部分（mxbM，mxbD和mxaB），并且只有mxbM和mxbD突变体会显着影响PQQ的最终水平。

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