1kba

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spinqualitylabelsall models 1kba, resolution 2.3Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

CRYSTAL STRUCTURE OF KAPPA-BUNGAROTOXIN AT 2.3-ANGSTROM RESOLUTION

Overview

kappa-Neurotoxins display a very low affinity for neuromuscular receptors, but bind tightly to, and inhibit, nicotinic acetylcholine receptors in, neuronal tissue such as the chick ciliary ganglia. In contrast, alpha-neurotoxins bind with high affinity and inhibit nicotinic, acetylcholine receptors at the neuromuscular junction. The origin of this, difference in specificity has been a long-studied question in the field., Here we report the first crystal structure of a kappa-neurotoxin, kappa-bungarotoxin. Unlike the NMR structure previously reported, [Sutcliffe, M. J., Dobson, C. M., & Oswald, R. E. (1992) Biochemistry 31, 2962-2970], the present crystal structure more accurately defines the, polypeptide fold and the nature of the interaction between subunits in the, active dimer, which is a unique feature of the kappa-neurotoxins. The, structure has been refined to R = 19.6% with X-ray diffraction data, extending to a resolution of 2.3 A. There are two independent protein, molecules (66 amino acid residues each) in the asymmetric unit that are, arranged as a dimer with the two subunits related by a rotation of 178.6, degrees. Each subunit consists of three main-chain loops. Three of the, five beta-strands of each subunit form an antiparallel beta-sheet which, becomes an extended six-stranded antiparallel beta-sheet, by virtue of the, approximate 2-fold symmetry of the dimer. The interactions at the dimer, interface consist of six main-chain-main-chain hydrogen bonds, as well as, three other hydrogen-bonding interactions involving side chains.(ABSTRACT, TRUNCATED AT 250 WORDS)

About this Structure

1KBA is a Single protein structure of sequence from Bungarus multicinctus. Full crystallographic information is available from OCA.

Reference

Crystal structure of kappa-bungarotoxin at 2.3-A resolution., Dewan JC, Grant GA, Sacchettini JC, Biochemistry. 1994 Nov 8;33(44):13147-54. PMID:7947721

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