| Summary: | 碩士 === 國立陽明大學 === 生化暨分子生物研究所 === 101 === The lutABC operon of Bacillus subtilis RO-NN-1 encodes three iron-sulfur-containing proteins reguired for L-lactate utilization. Expression of the lutABC operon is under the dual control of LutR (a GntR-type repressor) and SinR (the master regulator for biofilm formation). In this study, we identified an inverted repeat sequence in the lutA promoter region as the LutR operator. We also mapped the transcriptional start site of the lutABC operon by primer extension analysis. The lutP gene, which is divergently transcribed from lutR, encodes a lactate transporter for L-lactate uptake. However, the regulatory mechanism for lutP expression is unknown. We now demonstrate that lutP transcription is also under the negative control of LutR. We have identified a LutR-binding site in the lutP promoter region. We found that L-lactate could dramatically induce lutP expression and disruption of the lutR gene led to highly constitutive expression of lutP. Results from electrophoretic mobility shift assays suggest that L-lactate, pyruvate, L-alanine, and acetyl-CoA are not a direct inducer for expression of lutA and lutP. In contrast to strain RO-NN-1 of B. subtilis, the strain 168 probably produces a defective LutR repressor which is deficient in repressing transcription of lutA and lutP.
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