Properties of radiolabeled α-bungarotoxin derivatives and their interaction with nicotinic acetylcholine receptors

Publisher Website
Google Scholar
Abstract
Column-purified monoiodinated, diiodinated and tritiated derivatives of .alpha.-bungarotoxin (.alpha.-Bgt) were distinguished on the basis of their UV absorption and circular dichroism (CD) spectra. The pattern of changes in CD spectra on incorporation of I into a single tyrosine residue of .alpha.-Bgt and the widespread wavelength distribution of these effects were interpreted as reflecting primary chemical modification of the tyrosine chromophore and vicinal and global secondary structural changes. Native and tritiated .alpha.-Bgt were more effective than iodinated .alpha.-Bgt derivatives in competing for specific toxin binding sites on putative nicotinic acetylcholine receptors (nAChR) derived from rat brain, reflecting functional perturbation of the modified toxin. Membrane-bound and solubilized nAChR from Torpedo californica electroplax displayed little or no specific binding preference for native toxin, nor are there significant differences in lethal potency of .alpha.-Bgt derivatives towards mice. Peripheral and putative central nAChR may differ in their .alpha.-Bgt binding properties, and modified toxin seems to be useful in detecting those subtle differences.