tailieunhanh - Báo cáo khoa học: The N-terminal hybrid binding domain of RNase HI from Thermotoga maritima is important for substrate binding and Mg2+-dependent activity

Thermotoga maritimaribonuclease H (RNase H) I (Tma-RNase HI) con-tains a hybrid binding domain (HBD) at the N-terminal region. To analyze the role of this HBD, Tma-RNase HI, Tma-W22A with the single mutation at the HBD, the C-terminal RNase H domain (Tma-CD) and the N-termi-nal domain containing the HBD (Tma-ND) were overproduced inEscheri-chia coli, purified and biochemically characterized. | ễFEBS Journal The N-terminal hybrid binding domain of RNase HI from Thermotoga maritima is important for substrate binding and Mg2 -dependent activity Nujarin Jongruja1 Dong-Ju You1 Eiko Kanaya1 Yuichi Koga1 Kazufumi Takano1 2 and Shigenori Kanaya1 1 Department of Materialand Life Science Graduate Schoolof Engineering Osaka University Japan 2 CRESTO JST Osaka Japan Keywords cleavage site specificity hybrid binding domain metal preference RNase H substrate binding affinity Thermotoga maritima Correspondence S. Kanaya Department of Materialand Life Science Graduate School of Engineering Osaka University 2-1 Yamadaoka Suita Osaka 565-0871 Japan Fax 81 6 6879 7938 Tel. 81 6 6879 7938 E-mail kanaya@ Received 18 June 2010 revised 6 August 2010 accepted 27 August 2010 doi Thermotoga maritima ribonuclease H RNase H I Tma-RNase HI contains a hybrid binding domain HBD at the N-terminal region. To analyze the role of this HBD Tma-RNase HI Tma-W22A with the single mutation at the HBD the C-terminal RNase H domain Tma-CD and the N-termi-nal domain containing the HBD Tma-ND were overproduced in Escherichia coli purified and biochemically characterized. Tma-RNase HI prefers Mg2 to Mn2 for activity and specifically loses most of the Mg2 -dependent activity on removal of the HBD and 87 of it by the mutation at the HBD. Tma-CD lost the ability to suppress the RNase H deficiency of an E. coli rnhA mutant indicating that the HBD is responsible for in vivo RNase H activity. The cleavage-site specificities of Tma-RNase HI are not significantly changed on removal of the HBD regardless of the metal cofactor. Binding analyses of the proteins to the substrate using surface plasmon resonance indicate that the binding affinity of Tma-RNase HI is greatly reduced on removal of the HBD or the mutation. These results indicate that there is a correlation between Mg2 -dependent activity and substrate binding affinity. Tma-CD was as stable as .