title: Use of the α-mannosidase I inhibitor kifunensine allows the crystallization of apo CTLA-4 homodimer produced in long-term cultures of Chinese hamster ovary cells.
abstract: Glycoproteins present problems for structural analysis since they often have to be glycosylated in order to fold correctly and because their chemical and conformational heterogeneity generally inhibits crystallization. It is shown that the α-mannosidase I inhibitor kifunensine, which has previously been used for the purpose of glycoprotein crystallization in short-term (3-5 d) cultures, is apparently stable enough to be used to produce highly endoglycosidase H-sensitive glycoprotein in long-term (3-4 week) cultures of stably transfected Chinese hamster ovary (CHO) cells. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry-based analysis of the extracellular region of the cytotoxic T-lymphocyte antigen 4 (CTLA-4; CD152) homodimer expressed in long-term CHO cell cultures in the presence of kifunensine revealed that the inhibitor restricted CTLA-4 glycan processing to Man9GlcNAc2 and Man5GlcNAc2 structures. Complex-type glycans were undetectable, suggesting that the inhibitor was active for the entire duration of the cultures. Endoglycosidase treatment of the homodimer yielded protein that readily formed orthorhombic crystals with unit-cell parameters a=43.9, b=51.5, c=102.9 Å and space group P2(1)2(1)2(1) that diffracted to Bragg spacings of 1.8 Å. The results indicate that kifunensine will be effective in most, if not all, transient and long-term mammalian cell-based expression systems.
authors.affiliation: Nuffield Department of Clinical Medicine, University of Oxford, John Radcliffe Hospital, Headington, Oxford OX3 9DS, England.
authors.forename: Chao
authors.initials: C
authors.lastname: Yu
authors.forename: Max
authors.initials: M
authors.lastname: Crispin
authors.forename: Andreas F-P
authors.initials: AF
authors.lastname: Sonnen
authors.forename: David J
authors.initials: DJ
authors.lastname: Harvey
authors.forename: Veronica T
authors.initials: VT
authors.lastname: Chang
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Evans
authors.forename: Christopher N
authors.initials: CN
authors.lastname: Scanlan
authors.forename: David I
authors.initials: DI
authors.lastname: Stuart
authors.forename: Robert J C
authors.initials: RJ
authors.lastname: Gilbert
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Davis
mesh_terms: D000470:Alkaloids / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D015703:Antigens, CD / Q000737:chemistry* / Q000378:metabolism; D001059:Apoproteins / Q000737:chemistry* / Q000378:metabolism; D016466:CHO Cells; D060908:CTLA-4 Antigen; D006224:Cricetinae; D003412:Cricetulus; D003460:Crystallization; D006801:Humans; D011134:Polysaccharides; D011485:Protein Binding; D055503:Protein Multimerization; D043323:alpha-Mannosidase / Q000037:antagonists & inhibitors
chemical_list: D000470:Alkaloids; D015703:Antigens, CD; D001059:Apoproteins; D060908:CTLA-4 Antigen; C556706:CTLA4 protein, human; D011134:Polysaccharides; C065629:kifunensine; D043323:alpha-Mannosidase