A gene from the Sec2 (Gli-R2) locus of a wheat 2RS.2BL chromosomal translocation line

A genomic DNA clone coding for a rye secalin gene (gSec2A) was isolated fro m a wheat translocation line carrying the 2RS.2BL chromosome, using a previ ously identified partial secalin (Sec2) cDNA clone as a probe. The predicte d N-terminal amino-acid sequence of the gSec2A gene was identical to the N- terminal sequence obtained for Sec2 polypeptide bands isolated from SDS-PAG E gels. Bacterially expressed gSec2A protein was identical in size to that of the smallest Sec2 polypeptide band observed on SDS PAGE gels and is reco gnized by a monoclonal antibody specific for Mr 75000 2RS gamma -secalins. Overall, the predicted protein sequence of gSec2A was most similar (50%) to the family of gamma -gliadins and consists of a short N-terminal region co ntaining one cysteine residue followed by a glutamine/proline-rich repetiti ve domain and a long C-terminal domain containing eight cysteine residues. The repetitive domain can be divided into two regions. One region coded for 15 units, each consisting of eight amino acids similar in sequence to that found in the omega -secalins and C-hordeins. The second region coded for 1 7 units each consisting of a sequence of 7-10 amino acids similar to that o bserved in gamma -gliadins.