tailieunhanh - Báo cáo khoa học: X-ray crystallography and structural stability of digestive lysozyme from cow stomach

In ruminants, some leaf-eating animals, and some insects, defensive lyso-zymes have been adapted to become digestive enzymes, in order to digest bacteria in the stomach. Digestive lysozyme has been reported to be resis-tant to protease and to have optimal activity at acidic pH. The structural basis of the adaptation providing persistence of lytic activity under severe gastric conditions remains unclear. | X-ray crystallography and structural stability of digestive lysozyme from cow stomach Yasuhiro Nonaka1 Daisuke Akieda1 Tomoyasu Aizawa1 Nobuhisa Watanabe1 2 Masakatsu Kamiya3 Yasuhiro Kumaki1 Mineyuki Mizuguchi4 Takashi Kikukawa1 Makoto Demura3 and Keiichi Kawano1 1 Division of BiologicalSciences Graduate Schoolof Science Hokkaido University Sapporo Japan 2 Department of Biotechnology and BiomaterialChemistry Graduate Schoolof Engineering Nagoya University Nagoya Japan 3 Division of Molecular Life Science Graduate Schoolof Life Science Hokkaido University Sapporo Japan 4 Graduate Schoolof Medicine and PharmaceuticalSciences University of Toyama Toyama Japan Keywords lysozyme molecular evolution protease resistance structuralstability X-ray crystallography Correspondence K. Kawano Graduate School of Science Hokkaido University North 10 West 8 Kita-ku Sapporo Hokkaido 060 0810 Japan Fax 81 11 706 2770 Tel 81 11 706 2770 E-mail kawano@ Received 12 November 2008 revised 22 January 2009 accepted 4 February 2009 doi In ruminants some leaf-eating animals and some insects defensive lysozymes have been adapted to become digestive enzymes in order to digest bacteria in the stomach. Digestive lysozyme has been reported to be resistant to protease and to have optimal activity at acidic pH. The structural basis of the adaptation providing persistence of lytic activity under severe gastric conditions remains unclear. In this investigation we obtained the crystallographic structure of recombinant bovine stomach lysozyme 2 BSL2 . Our denaturant and thermal unfolding experiments revealed that BSL2 has high conformational stability at acidic pH. The high stability in acidic solution could be related to pepsin resistance which has been previously reported for BSL2. The crystal structure of BSL2 suggested that negatively charged surfaces a shortened loop and salt bridges could provide structural stability and thus resistance to .