[Structure of peptide fragments of the complex (Lys(Abz)26) neurotoxin II from Naja naja oxiana cross-linked with the nicotinic acetylcholine receptor from Torpedo californica]. / Struktura peptidnykh fragmentov kross-sshitogo kompleksa (Lys(Abz)26)neurotoksina II Naja naja oxiana s nikotinovym atsetilkholinovym retseptorom iz Torpedo californica.

After irradiating the acetylcholine receptor complex with the title neurotoxin derivative, the labeled delta-subunit was separated by preparative SDS-PAGE, reduced-carboxymethylated and cleaved with LysC endoproteinase. One of the radioactive peptides isolated by HPLC was further purified by electrophoresis in a tricin gel. Edman degradation of the radioactive fractions yielded the sequence of the delta-subunit fragment starting from Phe148. The AspN-cleavage of the radioactive peptide from the LysC digest gave on HPLC a radioactive peak which eluted similarly to peptide 33-44 generated by LysC/AspN-cleavage of 125I-neurotoxin II. In model experiments, irradiation of the photoactivable derivative was found to produce a heterogeneous mixture of reaction products. Unusually low initial and repetitive yields were observed for neurotoxin II and its fragments containing the photolabeled and radiolabeled residues. These results might explain why the neurotoxin sequence was not detected on Edman degradation of the cross-linked products available at a low picomole level.