Characterization of the β-ketoadipate pathway in Sinorhizobium meliloti
Characterization of the β-ketoadipate pathway in Sinorhizobium meliloti
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DOI：
10.1128/aem.00580-06
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发表时间：
2006-08-01
影响因子：
4.4
通讯作者：
Finan, Turlough M.
中科院分区：
文献类型：
--
作者：
MacLean, Allyson A.;MacPherson, Gordon;Finan, Turlough M.
芳香族化合物是土壤生物重要的能量来源。的P-酮己二酸途径是一个关键的代谢途径，参与catenophase的芳香族化合物原儿茶酸和儿茶酚，在这里，我们通过酶分析和突变体分析表明，生长和catenophase的原儿茶酸在土壤中所需的基因苜蓿中华根瘤菌组织pSymB megaplastic在两个转录单位指定pcaDCHGB和pcaIJF。pcaD启动子映射引物延伸，从这个启动子的表达被证明是受LysR型蛋白PcaQ。β-酮己二酸琥珀酰辅酶A（CoA）转移酶活性。苜蓿草被证明是由SMB 20587和SMB 20588编码的，并且这些基因已分别被重命名为pcaI和pcaJ。这些基因与推定的β-酮己二酰-CoA硫解酶基因（pcaF）一起被组织在操纵子中，并且pcaF操纵子的表达显示出受IclR型转录调节因子SMB 20586（我们将其命名为pcaR）调节。我们发现，pcaR转录是负自调节的，PcaR是pcaIJF表达的正调节因子，是S.草木犀以原儿茶酸为碳源。对S.苜蓿提供了与包括根癌农杆菌在内的相关物种进行比较的机会。在S. meliloti和苜蓿A.根瘤菌pcaU提供了豌豆基因的第一个证据，这些豌豆基因可能是在这些密切相关的物种形成后获得的。
Aromatic compounds represent an important source of energy for soil-dwelling organisms. The P-ketoadipate pathway is a key metabolic pathway involved in the catabolism of the aromatic compounds protocatechuate and catechol, and here we show through enzymatic analysis and mutant analysis that genes required for growth and catabolism of protocatechuate in the soil-dwelling bacterium Sinorhizobium meliloti are organized on the pSymB megaplasmid in two transcriptional units designated pcaDCHGB and pcaIJF. The pcaD promoter was mapped by primer extension, and expression from this promoter is demonstrated to be regulated by the LysR-type protein PcaQ. beta-Ketoadipate succinyl-coenzyme A (CoA) transferase activity in S. meliloti was shown to be encoded by SMb20587 and SMb20588, and these genes have been renamed pcaI and pcaJ, respectively. These genes are organized in an operon with a putative beta-ketoadipyl-CoA thiolase gene (pcaF), and expression of the pcaIJF operon is shown to be regulated by an IclR-type transcriptional regulator, SMb20586, which we have named pcaR. We show that pcaR transcription is negatively autoregulated and that PcaR is a positive regulator of pcaIJF expression and is required for growth of S. meliloti on protocatechuate as the carbon source. The characterization of the protocatechuate catabolic pathway in S. meliloti offers an opportunity for comparison with related species, including Agrobacterium tumefaciens. Differences observed between S. meliloti and A. tumefaciens pcaU offer the first evidence of pea genes that may have been acquired after speciation in these closely related species.