Molecular analysis of the glucose-specific phosphoenolpyruvate : sugar phosphotransferase system from Lactobacillus casei and its links with the control of sugar metabolism.
Molecular analysis of the glucose-specific phosphoenolpyruvate : sugar phosphotransferase system from Lactobacillus casei and its links with the control of sugar metabolism.
复制标题
葡萄糖特异性磷酸烯醇丙酮酸的分子分析：干酪乳杆菌的糖磷酸转移酶系统及其与糖代谢控制的联系。
作者：
M. J. Yebra;V. Monedero;M. Zúñiga;J. Deutscher;G. Pérez
Lactobacillus casei transports glucose preferentially by a mannose-class phosphoenolpyruvate : sugar phosphotransferase system (PTS). The genomic analysis of L. casei allowed the authors to find a gene cluster (manLMNO) encoding the IIAB (manL), IIC (manM) and IID (manN) proteins of a mannose-class PTS, and a putative 121 aa protein of unknown function (encoded by manO), homologues of which are also present in man clusters that encode glucose/mannose transporters in other Gram-positive bacteria. The L. casei man operon is constitutively expressed into a manLMNO messenger, but an additional manO transcript was also detected. Upstream of the man operon, two genes (upsR and upsA) were found which encode proteins resembling a transcriptional regulator and a membrane protein, respectively. Disruption of either upsR or upsA did not affect manLMNO transcription, and had no effect on glucose uptake. Cells carrying a manO deletion transported glucose at a rate similar to that of the wild-type strain. By contrast, a manM disruption resulted in cells unable to transport glucose by the PTS, thus confirming the functional role of the man genes. In addition, the manM mutant exhibited neither inducer exclusion of maltose nor glucose repression. This result confirms the need for glucose transport through the PTS to trigger these regulatory processes in L. casei.
