Crystallographic studies on human BST-1/CD157 with ADP-ribosyl cyclase and NAD glycohydrolase activities.
cADPR is the novel second messenger that elicits calcium release from intracellular calcium stores and works independently of IP(3). In mammals, the ADP-ribosyl cyclase function is found in two membrane proteins, CD38 and BST-1/CD157. These enzymes, exposed extracellularly, bear cADPR hydrolase and NAD glycohydrolase activities. In spite of its functional importance, the structural basis of these enzymatic reactions remains elusive. We determined the crystal structures of the extracellular region of human BST-1 at atomic resolution in the free form and in complexes with five substrate analogues: nicotinamide, NMN, ATPgammaS, ethenoNADP, and ethenoNAD. The three-dimensional structural views of the reaction centre with these ligands revealed the mode of substrate binding and the catalytic mechanism of the multifunctional enzymatic reactions. In each catalytic cleft of the dimeric enzyme, substrates are recognized predominantly through van der Waals interactions with two tryptophan residues, and thereby the N-glycosidic bond of NAD is correctly exposed near a catalytic glutamate residue. Its carboxyl side-chain stabilizes the catalytic intermediate of the S(N)-1 type reaction. This conformation of the catalytic cleft also implies the mechanism of cyclization between the adenine base and the ribose. The three key residues are invariant among the sequences of BST-1, CD38, and Aplysia cyclase, and hence this substrate recognition mode and catalytic scheme appear to be common in the cyclase family.
Yamamoto-Katayama
Sumie
S
Department of Molecular Biology, Research Institute (BERI), Suita-City, Osaka, Japan.
Ariyoshi
Mariko
M
Ishihara
Katsuhiko
K
Hirano
Toshio
T
Jingami
Hisato
H
Morikawa
Kosuke
K
D036541:ADP-ribosyl Cyclase; D051997:ADP-ribosyl Cyclase 1; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism; D000595:Amino Acid Sequence; D015703:Antigens, CD; D000943:Antigens, Differentiation / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D018360:Crystallography, X-Ray; D019281:Dimerization; D004220:Disulfides / Q000378:metabolism; D058851:GPI-Linked Proteins; D006801:Humans; D008024:Ligands; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000378:metabolism*; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009243:NAD / Q000031:analogs & derivatives; D009244:NAD+ Nucleosidase / Q000737:chemistry / Q000378:metabolism*; D009249:NADP / Q000031:analogs & derivatives; D009536:Niacinamide / Q000378:metabolism; D009537:Nicotinamide Mononucleotide / Q000378:metabolism; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D013379:Substrate Specificity
D015703:Antigens, CD; D000943:Antigens, Differentiation; D004220:Disulfides; D058851:GPI-Linked Proteins; D008024:Ligands; D008562:Membrane Glycoproteins; D009243:NAD; D009537:Nicotinamide Mononucleotide; D009536:Niacinamide; C022571:adenosine 5'-O-(3-thiotriphosphate); D009249:NADP; D000255:Adenosine Triphosphate; D036541:ADP-ribosyl Cyclase; C087521:ADP-ribosyl cyclase 2; C498154:CD38 protein, human; D009244:NAD+ Nucleosidase; D051997:ADP-ribosyl Cyclase 1