Journal of Biochemistry Advance Access published online on March 11, 2009
Journal of Biochemistry, doi:10.1093/jb/mvp047
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Crystallographic Snapshots of an Entire Reaction Cycle for a Retaining Xylanase from Streptomyces Olivaceoviridis E-86
1Department of Material and Biological Chemistry, Faculty of Science, Yamagata University, Yamagata 990-8560, Japan
2Protein Research Unit, National Institute of Agrobiological Sciences, Tsukuba 305-8602, Japan
3Gene Function Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8562, Japan
4Food Biotechnology Division, National Food Research Institute, Tsukuba 305-8642, Japan
5Department of Chemistry and Biotechnology, School of Engineering, University of Tokyo, Tokyo 113-8656, Japan
6Tokyo University and Graduate School of Social Welfare, Isesaki, Gunma 372-0831, Japan
7Nagase & Co., Ltd., Nihonbashi, Tokyo 103-8355, Japan
8Research Center for Medical Glycoscience, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8568, Japan
*To whom correspondence should be addressed: Atsushi Kuno. Research Center for Medical Glycoscience, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 2, 1-1-1 Umezono, Tsukuba 305-8568, Japan. Tel: +81-29-861-3187; Fax: +81-29-861-3125; E-mail: atsu-kuno{at}aist.go.jp
Received December 7, 2008; Accepted February 28, 2009
| Abstract |
|---|
Retaining glycosyl hydrolases, which catalyze both glycosylation and deglycosylation in a concerted manner, are the most abundant hydrolases. To date, their visualization has tended to be focused on glycosylation because glycosylation reactions can be visualized by inactivating deglycosylation step and/or using substrate analogues to isolate covalent intermediates. Furthermore, during structural analyses of glycosyl hydrolases with hydrolytic reaction products by the conventional soaking method, mutarotation of an anomeric carbon in the reaction products promptly and certainly occurs. This undesirable structural alteration hinders visualization of the second step in the reaction. Here, we investigated X-ray crystallographic visualization as a possible method for visualizing the conformational itinerary of a retaining xylanase from Streptomyces olivaceoviridis E-86. To clearly define the stereochemistry at the anomeric carbon during the deglycosylation step, extraneous nucleophiles, such as azide, were adopted to substitute for the missing base catalyst in an appropriate mutant. The X-ray crystallographic visualization provided snapshots of the components of the entire reaction, including the ES complex, the covalent intermediate, breakdown of the intermediate and the EP complex.
Key Words: Crystallographic visualization, retaining GH10 β-xylanase, switching enzyme with azide, molecular evolution, chemical rescue
#deceased on 1 December, 2004.