© 2006 The Japanese Biochemical Society.
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Analysis of Internal Motions of RNase T1 Complexed with a Productive Substrate Involving 15N NMR Relaxation Measurements
1 Department of Immunology, 2 Department of Pharmaceutical Synthetic Chemistry, and 3 NMR Section, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582; and 4 Faculty of Biotechnology and Life Science, Sojo University, Kumamoto 860-0082
* To whom correspondence should be addressed. Tel: +81-92-642-6662, Fax: +81-92-642-6667, E-mail: ueda{at}phar.kyushu-u.ac.jp
The backbone dynamics of RNase T1 in the presence of exo-guanosine 2',3'-cyclophosphorothioate (exo-cGPS isomer), which is a productive substrate, and in the presence of 3'-guanylic acid (3'GMP), which is an nonproductive substrate, were examined using 15N nuclear magnetic resonance. Although the X-ray crystal structure suggests that the modes of binding of these substrates to the active-site cleft are very similar, the order parameters in a number of regions in RNase T1 complexed with exo-cGPS isomer were different from those with 3'GMP. Moreover, the chemical exchange in line width observed for RNase T1 complexed with exo-cGPS isomer was also different from that observed for RNase T1 complexed with 3'GMP. From these results, we concluded that the internal motions in RNase T1 complexed with a productive substrate were not always identical to those in RNase T1 complexed with a nonproductive substrate.