Characterization and Molecular Mechanism of AroP as an Aromatic Amino Acid and Histidine Transporter in Corynebacterium glutamicum----中国科学院微生物研究所

科研成果

论文题目:	Characterization and Molecular Mechanism of AroP as an Aromatic Amino Acid and Histidine Transporter in Corynebacterium glutamicum
作者:	Shang Xiuling#, Zhang Yun#, Zhang Guoqiang, Chai Xin, Deng Aihua, Liang Yong, Wen Tingyi*
联系作者:	Wen Tingyi*
刊物名称:	Journal of Bacteriology
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年份:	2013
影响因子:	3.593
论文下载:	http://jb.asm.org/content/early/2013/09/16/JB.00971-13.longShang
摘要:	Corynebacterium glutamicum is equipped with abundant membrane transporters to adapt to a changing environment. Many amino acid transporters have been identified in C. glutamicum, however, histidine uptake has not been investigated in detail. Here we identified the aromatic amino acid transporter encoded by aroP as a histidine transporter in C. glutamicum by combination of the growth and histidine uptake features. Characterization of histidine uptake showed that AroP has a moderate affinity for histidine with Km value of 11.40 +/- 2.03 muM and histidine uptake by AroP is competitively inhibited by the aromatic amino acids. Among the four substrates, AroP exhibits a stronger preference for tryptophan over tyrosine, phenylalanine and histidine. Homology structure modeling and molecular docking were performed to predict the substrate binding modes and conformational changes during substrate transport. These results suggested that tryptophan is best accommodated in the binding pocket due to shape compatibility, strong hydrophobic interactions and the lowest binding energy, which is consistent with the observed substrate preference of AroP. Furthermore, the missense mutations of the putative substrate binding sites verified that Ser24, Ala28 and Gly29 play crucial roles in substrate binding and are highly conserved in the Gram-positive bacteria. Finally, the expression of aroP is not significantly affected by extracellular histidine or aromatic amino acids, indicating that the physiological role of AroP may be correlated with the increased fitness of C. glutamicum to assimilate extracellular amino acid for avoiding high energy cost of amino acid biosynthesis.