Crystal Structure of Concanavalin B at 1.65 Å Resolution. An "Inactivated" Chitinase from Seeds ofCanavalia ensiformis

Michael Hennig, Johan N. Jansonius, Anke C. Terwisscha van Scheltinga, Bauke W. Dijkstra, Bernhard Schlesier
1995 Journal of Molecular Biology  
Seeds of Canavalia ensiformis (jack bean) contain besides large amounts of 1 Department of Structural canavalin and concanavalin A, a protein with a molecular mass of 33,800 Biology, Biozentrum which has been named concanavalin B. Although concanavalin B shares University of Basel Klingelbergstr. 70, 4056 about 40% sequence identity with plant chitinases belonging to glycosyl hydrolase family 18, no chitinase activity could be detected for this protein. Basel, Switzerland To resolve this
more » ... uity concanavalin B was crystallised and its 2 BIOSON Research Institute three-dimensional structure determined at 1.65 Å (1 Å = 0.1 nm) resolution. and Laboratory of Biophysical The structure consists of a single domain with a (b/a) 8 topology. A 30 amino Chemistry, University of acid residue long loop occurs between the second b-strand of the barrel and Groningen, Nijenborgh 4 the second a-helix. This extended loop is unusual for the (b/a) 8 topology, 9747 AG Groningen but appears in a similar conformation in the structures of the seed protein The Netherlands narbonin and several chitinases as well. Two non-proline cis-peptide bonds are present in the structure of concanavalin B: Ser34-Phe, and Trp265-Asn. Institut fü r Pflanzengenetik This structural feature is rarely observed in proteins, but could also be und Kulturpflanzenforschung identified in the three-dimensional structures of family 18 chitinases and Corrensstr. 3, 06466 narbonin in coincident positions. In the chitinases the aromatic residues of Gatersleben, Germany the non-proline cis-peptides have been proposed to have a function in the binding of the substrate. The region in concanavalin B, where in chitinases the active site is located, shows two significant differences. First, the catalytic glutamic acid is a glutamine in concanavalin B. Second, although part of the substrate binding cleft of the chitinases is present in concanavalin B, it is much shorter. From this we conclude that concanavalin B and family 18 chitinases are closely related, but that concanavalin B has lost its enzymatic function. It still may act as a carbohydrate binding protein, however.
doi:10.1006/jmbi.1995.0614 pmid:7490746 fatcat:7hoeubemvfcj7a566exoqbcwlu