The Complete Amino Acid Sequence and Disulphide Bond Arrangement of Oat Alcohol‐soluble Avenin‐3

We have elucidated the complete amino acid sequence of one of the avenin 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 spectrometry. The protein is a single polypeptide chain, consisting of 201 amino acid residues with M r 23252.8. The N‐terminal amino acid residue of the protein is blocked with 5‐oxoproline (pyroglutamic acid). All 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 disulfide bonds (S‐S core). Subsequent subdigestion of this S‐S core allowed isolation of disulphide bonded peptides detected by differential reverse‐phase HPLC before and after reduction. As a result, all four disulphides , , and were identified. Comparison of avenins with other prolamins demonstrates 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 repeated sequence motifs.