title: Purification, characterization and preliminary crystallographic studies of a cysteine protease from Pachyrrhizus erosus seeds.
abstract: The proteins Spe31 and Spe32, named after their respective molecular weights of about 31 and 32 kDa, were purified simultaneously from the seeds of Pachyrrhizus erosus. They cannot be separated from each other by column chromatography. N-terminal sequence analysis indicated that they belonged to the papain family of cysteine proteases. An in-gel activity assay revealed that Spe31 possesses proteolytic activity while Spe32 only displays very weak activity for protein degradation. Both of them are glycoproteins as detected by the periodic acid and Schiff's reagent method. Crystals were obtained from the protein mixture by the hanging-drop vapour-diffusion method; they diffracted to a resolution of 2.61 A on an in-house X-ray source. The crystals belong to space group P4(1(3))2(1)2, with unit-cell parameters a = b = 61.96, c = 145.61 A. Gel electrophoresis under non-denaturing conditions showed that the protein crystallized was Spe31.
authors.affiliation: School of Life Sciences, University of Science and Technology of China, Key Laboratory of Structural Biology, Hefei, Anhui 230026, People's Republic of China.
authors.forename: Shaojie
authors.initials: S
authors.lastname: Chang
authors.forename: Xiaomin
authors.initials: X
authors.lastname: Song
authors.forename: Ming
authors.initials: M
authors.lastname: Yan
authors.forename: Zhaocai
authors.initials: Z
authors.lastname: Zhou
authors.forename: Fang
authors.initials: F
authors.lastname: Wu
authors.forename: Weimin
authors.initials: W
authors.lastname: Gong
mesh_terms: D000595:Amino Acid Sequence; D002848:Chromatography, DEAE-Cellulose; D003460:Crystallization; D018360:Crystallography, X-Ray; D003546:Cysteine Endopeptidases / Q000737:chemistry* / Q000302:isolation & purification; D006023:Glycoproteins / Q000378:metabolism; D008969:Molecular Sequence Data; D029905:Pachyrhizus / Q000201:enzymology*; D010940:Plant Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D012639:Seeds / Q000201:enzymology
chemical_list: D006023:Glycoproteins; D010940:Plant Proteins; D003546:Cysteine Endopeptidases