Solution structure of gamma-bungarotoxin: the functional significance of amino acid residues flanking the RGD motif in integrin binding.
Gamma-bungarotoxin, a snake venom protein isolated from Bungarus multicinctus, contains 68 amino acids, including 10 cysteine residues and a TAVRGDGP sequence at positions 30-37. The solution structure of gamma-bungarotoxin has been determined by nuclear magnetic resonance (NMR) spectroscopy. The structure is similar to that of the short-chain neurotoxins that contain three loops extending from a disulfide-bridged core. The tripeptide Arg-Gly-Asp (RGD) sequence is located at the apex of the flexible loop and is similar to that of other RGD-containing proteins. However, gamma-bungarotoxin only inhibits platelet aggregations with an IC50 of 34 microM. To understand its weak activity in inhibiting platelet aggregation, we mutated the RGD loop sequences of rhodostomin, a potent platelet aggregation inhibitor, from RIPRGDMP to TAVRGDGP, resulting in a 196-fold decrease in activity. In addition, the average Calpha-to-Calpha distance between R33 and G36 of gamma-bungarotoxin is 6.02 A, i.e., shorter than that of other RGD-containing proteins that range from 6.55 to 7.46 A. These results suggested that the amino acid residues flanking the RGD motif might control the width of the RGD loop. This structural difference may be responsible for its decrease in platelet aggregation inhibition compared with other RGD-containing proteins.
Shiu
Jia-Hau
JH
Department of Biochemistry, National Cheng Kung University College of Medicine, Tainan, Taiwan.
Chen
Chiu-Yueh
CY
Chang
Long-Sen
LS
Chen
Yi-Chun
YC
Chen
Yen-Chin
YC
Lo
Yu-Hui
YH
Liu
Yu-Chen
YC
Chuang
Woei-Jer
WJ
D000244:Adenosine Diphosphate / Q000494:pharmacology; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D002038:Bungarotoxins / Q000737:chemistry* / Q000378:metabolism*; D004220:Disulfides; D016023:Integrins / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D009498:Neurotoxins / Q000378:metabolism; D009842:Oligopeptides / Q000737:chemistry* / Q000378:metabolism; D010974:Platelet Aggregation / Q000187:drug effects; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D012996:Solutions / Q000737:chemistry
D002038:Bungarotoxins; D004220:Disulfides; D016023:Integrins; D009498:Neurotoxins; D009842:Oligopeptides; D012996:Solutions; D000244:Adenosine Diphosphate; C047981:arginyl-glycyl-aspartic acid