Madhusudhan K T, Huang N, Braswell E H, Sokatch J R
Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City 73190, USA.
J Bacteriol. 1997 Jan;179(1):276-9. doi: 10.1128/jb.179.1.276-279.1997.
BkdR is the positive transcriptional activator of the inducible bkd operon of Pseudomonas putida. Evidence is accumulating that L-branched-chain amino acids are the inducers of the operon, and the data obtained in this study show that they induce a conformational change in BkdR. Addition of L-branched-chain amino acids increased the susceptibility of BkdR to trypsin with the cleavage between Arg-51 and Gln-52 on the C-terminal side of the DNA-binding domain. L-Valine also caused an increased fluorescence emission intensity and produced significant changes in the circular dichroism spectrum of BkdR. Analytical ultracentrifugation confirmed earlier data obtained from gel filtration that BkdR was a tetramer with a Stokes radius of 32 +/- 3 A and an axial ratio of 2:1.
BkdR是恶臭假单胞菌可诱导型bkd操纵子的正转录激活因子。越来越多的证据表明，L-支链氨基酸是该操纵子的诱导物，本研究获得的数据表明它们会诱导BkdR发生构象变化。添加L-支链氨基酸会增加BkdR对胰蛋白酶的敏感性，在DNA结合结构域C端一侧的Arg-51和Gln-52之间发生切割。L-缬氨酸还会导致BkdR的荧光发射强度增加，并使其圆二色光谱产生显著变化。分析超速离心证实了早期从凝胶过滤获得的数据，即BkdR是一种四聚体，斯托克斯半径为32 +/- 3 Å，轴比为2:1。
