The complete primary structure of abrin-a B chain

AbstractThe complete 267 amino acid sequence of abrin-a B chain was determined by analysis of peptides obtained by digestion with trypsin, chymotrypsin, lysyl endopeptidase, Staphylacaccus aureus V8 protease and thermolysin. The sequence is not identical with that predicted previously by nucleotide sequencing, indicating the presence of isoforms of abrin. Comparison of the amino acid sequence of abrin-a B chain with that of ricin-D B chain reveals a high degree of sequence identity (59%). Abrin-a B chain appears to consist of two domains, each domain with subdomains (α, β, γ) of about 40 amino acid residues

A complex of rab3A, SNAP-25, VAMP/synaptobrevin-2 and syntaxins in brain presynaptic terminals

AbstractTwo monoclonal antibodies (SPM-1 and SPM-2) immunoprecipitate brain N-type calcium channels. On immunoaffinity chromatography of digitonin extracts of bovine brain membranes on SPM-1- and SPM-2-Sepharose, proteins of 36 (syntaxins A and B), 28 and 19 kDa are specifically retained by both columns. Here we show that the 19 and 28 kDa bands contain VAMP/synaptobrevin-2, and rab3A/smg25A and SNAP-25, respectively. Since SPM-1 and SPM-2 recognize only syntaxins and the 28 kDa band (rab3A/smg25A and SNAP-25), respectively, the results indicate that all these proteins form a complex. Our results suggest tight linkage between the components involved in neurotransmitter release