title: The purification of a cysteine-dependent NAD+ glycohydrolase activity from bovine erythrocytes and evidence that it exhibits a novel ADP-ribosyltransferase activity.
abstract: An NAD+:cysteine ADP-ribosyltransferase activity was purified from bovine erythrocytes on the assumption that, like pertussis toxin, the enzyme would exhibit a cysteine-dependent NAD+ glycohydrolase activity. A three-step purification procedure was developed involving (1) precipitation with 40% (NH4)2SO4, (2) binding to a cysteine-Sepharose affinity column, and (3) binding to an NAD+ affinity column. PAGE showed a single band of M(r) 45,000. The enzyme had been purified 47,000-fold and had a specific activity of 1900 nmol nicotinamide released/min per mg. A study of the kinetic properties of this enzyme showed saturation kinetics for cysteine (Km = 4.0 mM). The ability of this enzyme to ADP-ribosylate protein was investigated using re-sealed inverted bovine erythrocyte ghosts. Incubation of the purified enzyme with erythrocyte ghosts and [adenylate-32P]NAD+ led to the enhanced dose-dependent labelling of several proteins, a doublet of high M(r) and proteins of M(r) 60,000, 55,000 and 29,000, identified by autoradiography of separated proteins on SDS/PAGE. The enzyme-catalysed labelling of the major component at M(r) 55,000 was blocked by pre-treatment of the erythrocyte ghosts with N-ethymaleimide, a sulphydryl alkylating agent, and the label was released by mercuric ion, but not by hydroxylamine. These experiments suggested that a cysteine residue on the target protein had been mono-ADP-ribosylated. This supposition was further supported by identification of the mercf1p4ion-released radiolabelled product as ADP-ribose by HPLC, and the observation that free ADP-ribose was unable to modify the membrane target protein directly.
authors.affiliation: Department of Biochemistry, University of Edinburgh, Scotland, U.K.
authors.forename: B A
authors.initials: BA
authors.lastname: Saxty
authors.forename: S
authors.initials: S
authors.lastname: van Heyningen
mesh_terms: D036002:ADP Ribose Transferases; D000818:Animals; D002417:Cattle; D002846:Chromatography, Affinity; D002851:Chromatography, High Pressure Liquid; D003545:Cysteine / Q000494:pharmacology*; D004591:Electrophoresis, Polyacrylamide Gel; D004910:Erythrocyte Membrane / Q000378:metabolism; D004912:Erythrocytes / Q000201:enzymology*; D007700:Kinetics; D008970:Molecular Weight; D009243:NAD / Q000378:metabolism; D009244:NAD+ Nucleosidase / Q000097:blood* / Q000302:isolation & purification*; D011065:Poly(ADP-ribose) Polymerases / Q000097:blood* / Q000302:isolation & purification*; D013379:Substrate Specificity
chemical_list: D009243:NAD; D036002:ADP Ribose Transferases; D011065:Poly(ADP-ribose) Polymerases; D009244:NAD+ Nucleosidase; D003545:Cysteine