X-ray analyses of aspartic proteinases. The three-dimensional structure at 2.1 A resolution of endothiapepsin.

摘要: The molecular structure of endothiapepsin (EC 3.4.23.6), the aspartic proteinase from Endothia parasitica, has been refined to a crystallographic R-factor 0.178 at 2.1 A resolution. positions 2389 protein non-hydrogen atoms have determined and present model contains 333 solvent molecules. is bilobal, consisting two predominantly beta-sheet domains that are related by an approximate 2-fold axis. Of approximately 170 residues, 65 topologically equivalent when one lobe superimposed on other. Twenty beta-strands arranged as five beta-sheets connected regions involving 29 turns four helices. central sheet involves three antiparallel strands each organized around dyad Each further local passes through sheets sandwich relates motifs (a, b, c, d) followed helix or irregular helical region. Sheets 1N 1C, contain interpenetrating psi structures contributed c,d,d' c',d',d, which intralobe dyad. sheet, 2N 2C, formed extended beta-hairpins b,c b',c' fold above respectively, hydrogen-bonded Asp32 Asp215 interlobe form intricate network with neighbouring residues comprise most symmetrical part structure. side-chains active site aspartate held coplanar nearby main chain makes "fireman's grip" hydrogen-bonding network. Residues 74 83 a'N b'N in N-terminal beta-hairpin loop high thermal parameters. This "flap" projects over cleft shields Shells water molecules found surface molecule large channels observed within crystal. There only intermolecular contacts crystal packing stabilized many forming hydrogen bonds. three-dimensional be similar other fungal proteinases, penicillopepsin rhizopuspepsin. Even though sequence identities rhizopuspepsin 41% 51%, superposition these enzymes shows 237 (72%) root-mean-square distance 1.0 A.