title: Two-way traffic of glycoside hydrolase family 18 processive chitinases on crystalline chitin.
abstract: Processivity refers to the ability of synthesizing, modifying and degrading enzymes to catalyse multiple successive cycles of reaction with polymeric substrates without disengaging from the substrates. Since biomass polysaccharides, such as chitin and cellulose, often form recalcitrant crystalline regions, their degradation is highly dependent on the processivity of degrading enzymes. Here we employ high-speed atomic force microscopy to directly visualize the movement of two processive glycoside hydrolase family 18 chitinases (ChiA and ChiB) from the chitinolytic bacterium Serratia marcescens on crystalline β-chitin. The half-life of processive movement and the velocity of ChiA are larger than those of ChiB, suggesting that asymmetric subsite architecture determines both the direction and the magnitude of processive degradation of crystalline polysaccharides. The directions of processive movements of ChiA and ChiB are observed to be opposite. The molecular mechanism of the two-way traffic is discussed, including a comparison with the processive cellobiohydrolases of the cellulolytic system.
authors.affiliation: 1] Department of Biomaterial Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan [2] Advanced Low Carbon Technology Research and Development Program, Japan Science and Technology Agency, K's Gobancho 7, Gobancho, Chiyoda-ku, Tokyo 102-0076, Japan [3].
authors.forename: Kiyohiko
authors.initials: K
authors.lastname: Igarashi
authors.affiliation: 1] Department of Physics, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa 920-1192, Japan [2] Bio-AFM Frontier Research Center, College of Science and Engineering, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan [3].
authors.forename: Takayuki
authors.initials: T
authors.lastname: Uchihashi
authors.affiliation: Department of Biomaterial Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Taku
authors.initials: T
authors.lastname: Uchiyama
authors.affiliation: Department of Applied Biological Chemistry, Faculty of Agriculture, Niigata University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan.
authors.forename: Hayuki
authors.initials: H
authors.lastname: Sugimoto
authors.affiliation: 1] Department of Biomaterial Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan [2] Department of Plant and Environmental New Resources, College of Life Sciences, Kyung Hee University, 1 Seocheon-dong, Giheung-ku, Yongin-si, Gyeonggi-do 446-701, Republic of Korea.
authors.forename: Masahisa
authors.initials: M
authors.lastname: Wada
authors.affiliation: Department of Applied Biological Chemistry, Faculty of Agriculture, Niigata University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan.
authors.forename: Kazushi
authors.initials: K
authors.lastname: Suzuki
authors.affiliation: Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Shohei
authors.initials: S
authors.lastname: Sakuda
authors.affiliation: 1] Department of Physics, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa 920-1192, Japan [2] Bio-AFM Frontier Research Center, College of Science and Engineering, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
authors.forename: Toshio
authors.initials: T
authors.lastname: Ando
authors.affiliation: Department of Applied Biological Chemistry, Faculty of Agriculture, Niigata University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Watanabe
authors.affiliation: Department of Biomaterial Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Samejima
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D002686:Chitin / Q000378:metabolism*; D002688:Chitinases / Q000378:metabolism*; D018625:Microscopy, Atomic Force; D021381:Protein Transport; D012706:Serratia marcescens / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D002686:Chitin; D002688:Chitinases; C000601656:chitinase A, Serratia marcescens; C000601657:chitinase B, Serratia marcescens