Regulation of D-galacturonate metabolism in <i>Caulobacter crescentus</i>by HumR, a LacI-family transcriptional repressor
Regulation of D-galacturonate metabolism in <i>Caulobacter crescentus</i>by HumR, a LacI-family transcriptional repressor作者机构：Biology Department Santa Clara University 500 El Camino Real Santa Clara USA
出 版 物：《Advances in Bioscience and Biotechnology》 (生命科学与技术进展（英文）)
年 卷 期：2013年第4卷第10期
页 面：63-74页
学科分类：1002[医学-临床医学] 100214[医学-肿瘤学] 10[医学]
主 题：Caulobacter Galacturonate LacI
摘 要：The oligotrophic freshwater bacterium Caulobacter crescentus encodes a cluster of genes (CC_1487 to CC_1495) shown here to be necessary for metabolism of D-galacturonate, the primary constituent of pectin, a major plant polymer. Sequence analysis suggests that these genes encode a version of the bacterial hexuronate isomerase pathway. A conserved 14 bp sequence motif is associated with promoter regions of three operons within this cluster, and is conserved in homologous gene clusters in related alpha-Proteobacteria. Embedded in the hexuronate gene cluster is a gene (CC_1489) encoding a member of the LacI family of bacterial transcription factors. This gene product, designated here as HumR (hexuronate metabolism regulator), represses expression of the uxaA and uxaC operon promoters by binding to the conserved operator sequence. Repression is relieved in the presence of galacturonate or, to a lesser extent, by glucuronate. Other genes potentially involved in pectin degradation and hexuronate transport are also under the control of HumR. Adoption of a LacI-type repressor to control hexuronate metabolism parallels the regulation of xylose, glucose, and maltose utilization in C. crescentus, but is distinct from the use of GntR-type repressors to control pectin and hexuronate utilization in gamma-Proteobacteria such as Escherichia coli.
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