Inhibitor peptide SNP-1 binds to a soluble form of BST-1/CD157 at a 2:2 stoichiometry.
Recently we have identified a 15-mer peptide, SNP-1, by a random phage library that can bind to bone marrow stromal cell antigen-1 (BST-1)/CD157 [Sato, A., Yamamoto, S., Ishihara, K., Hirano, T. & Jingami, H. (1999) Biochem. J. 337, 491-496]. SNP-1 inhibits BST-1 ADP-ribosyl cyclase activity uncompetitively with a Ki value of 180 +/- 40 nM. In this study we analysed biophysically the SNP-1 binding to a soluble form of BST-1 (sBST-1). Equilibrium binding data of wild-type SNP-1 from surface plasmon resonance studies gave a Kd value of 500 +/- 35 nM. Titration calorimetry analysis showed that the binding reaction is exothermic at 20 degrees C. The values of Kd = 211 nM, enthalpy change, DeltaH = -18.68 kcal.mol-1, and saturated molar ratio of bound SNP-1 per sBST-1, N = 0.8 mol.mol-1 were obtained. On the basis of the molecular masses of SNP-1 and sBST-1 calculated by analytical ultracentrifugation, the stoichiometry of the binding was determined to be 2 : 2. Electron microscopy also revealed the dimer form of sBST-1. To delineate the core residue of SNP-1 responsible for binding, each amino acid residue has been replaced by alanine. A region from amino acid residues 7-12 appeared to be critical for the SNP-1 binding to sBST-1. The substitution of the first residue, His, to Ala led to a reduction in binding, suggesting that the N-terminal residue is also crucial.
Sato
A
A
Department of Molecular Biology, Nagoya University, Japan.
Yamamoto
S
S
Kajimura
N
N
Oda
M
M
Usukura
J
J
Jingami
H
H
D036541:ADP-ribosyl Cyclase; D051997:ADP-ribosyl Cyclase 1; D015703:Antigens, CD; D000943:Antigens, Differentiation / Q000737:chemistry*; D015374:Biosensing Techniques; D002151:Calorimetry; D002352:Carrier Proteins / Q000737:chemistry* / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000494:pharmacology; D058851:GPI-Linked Proteins; D036341:Intercellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000648:ultrastructure; D008854:Microscopy, Electron; D016296:Mutagenesis; D009244:NAD+ Nucleosidase / Q000737:chemistry*; D009842:Oligopeptides / Q000737:chemistry* / Q000494:pharmacology; D010455:Peptides; D011485:Protein Binding; D020349:Surface Plasmon Resonance; D013816:Thermodynamics; D014461:Ultracentrifugation
D015703:Antigens, CD; D000943:Antigens, Differentiation; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D058851:GPI-Linked Proteins; D036341:Intercellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D009842:Oligopeptides; D010455:Peptides; C121720:SNP-1 protein, synthetic; D036541:ADP-ribosyl Cyclase; C087521:ADP-ribosyl cyclase 2; D009244:NAD+ Nucleosidase; D051997:ADP-ribosyl Cyclase 1