THE COMPLETE AMINO-ACID-SEQUENCE AND DISULFIDE BOND ARRANGEMENT OF OAT ALCOHOL-SOLUBLE AVENIN-3

We have elucidated the complete amino acid sequence of one of the aven in components, avenin-3, isolated from oat (Avena sativa L.), variety Narymsky 943. The sequence of the protein was determined by sequencing of CNBr and trypsin-generated peptides in combination with mass spect rometry. The protein is a single polypeptide chain, consisting of 201 amino acid residues with M(r) 23252.8. The N-terminal amino acid resid ue of the protein is blocked with 5-oxoproline (pyroglutamic acid). Al l eight cysteine residues in avenin-3 are involved in disulphide bonds . The positions of these bonds were established by identification of a CNBr cleavage product of the intact avenin containing all the disulfi de bonds (S-S core). Subsequent subdigestion of this S-S core allowed isolation of disulphide bonded peptides detected by differential rever se-phase HPLC before and reverse after reduction. As a result, all fou r disulphides Cys50 Cys183, Cys58 Cys77, Cys84 Cys85 and Cys97 Cys191 were identified. Comparison of avenins with other prolamins demonstrat es a high degree of similarity, which is especially pronounced around the cysteine residues. Avenins differ slightly from other prolamins in having unique N-terminal sequences and some differences in the repeat ed sequence motifs.