title: ADP-ribosyl cyclase; crystal structures reveal a covalent intermediate.
abstract: ADP-ribosyl cyclase catalyzes the elimination of nicotinamide from NAD and cyclization to cADPR, a known second messenger in cellular calcium signaling pathways. We have determined to 2.0 A resolution the structure of Aplysia cyclase with ribose-5-phosphate bound covalently at C3' and with the base exchange substrate (BES), pyridylcarbinol, bound to the active site. In addition, further refinement at 2.4 A resolution of the structure of nicotinamide-bound cyclase, which was previously reported, reveals that ribose-5-phosphate is also covalently bound in this structure, and a second nicotinamide site was identified. The structures of native and mutant Glu179Ala cyclase were also solved to 1.7 and 2.0 A respectively. It is proposed that the second nicotinamide site serves to promote cyclization by clearing the active site of the nicotinamide byproduct. Moreover, a ribosylation mechanism can be proposed in which the cyclization reaction proceeds through a covalently bound intermediate.
authors.affiliation: Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853 USA.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Love
authors.forename: Doletha M E
authors.initials: DM
authors.lastname: Szebenyi
authors.forename: Irina A
authors.initials: IA
authors.lastname: Kriksunov
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Thiel
authors.forename: Cyrus
authors.initials: C
authors.lastname: Munshi
authors.forename: Richard
authors.initials: R
authors.lastname: Graeff
authors.forename: Hon Cheung
authors.initials: HC
authors.lastname: Lee
authors.forename: Quan
authors.initials: Q
authors.lastname: Hao
mesh_terms: D036541:ADP-ribosyl Cyclase / Q000737:chemistry* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001048:Aplysia / Q000201:enzymology; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D008969:Molecular Sequence Data; D009537:Nicotinamide Mononucleotide / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012267:Ribosemonophosphates / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D012267:Ribosemonophosphates; D009537:Nicotinamide Mononucleotide; C031626:ribose-5-phosphate; D036541:ADP-ribosyl Cyclase