When alcohol extracts were assayed by a modified RP-HPLC gradient, peak 1 from some inbreds eluted at 25.79 min, while that from other lines eluted an average of 0.37 min later. The early-eluting C-zein came from inbreds with the slow SDS-PAGE variant. C-zeins from two pairs of inbreds, B57-N28 and Oh43-W64A, and from their reciprocal F1 hybrid seeds were assayed by RP-HPLC. As expected, double peaks occurred in the F1 extracts, with the higher peak corresponding to that of the maternal parent. N28 and W64A have the slow SDS-PAGE C-zein band and the first HPLC peak, while B57 and Oh43 have the fast SDS-PAGE band and the second HPLC peak. Other inbreds with the slow SDS-PAGE variant include B37, BSSS-53, B84, L289, Oh45, Pa91, R802, Va35, and WF9; the fast variant also occurs in A619, B14A, B68, B73, M14, Mo17, R801, and W22.
HPLC is thus a convenient assay for identification of C-zein variants among inbreds and segregating populations. A manuscript is in preparation describing how the same HPLC system has identified additional variation among major A- and B-zeins, which were previously identified by IEF and SDS-PAGE.
A single nucleotide change in the DNA
for C-zein could convert glutamine into a hydrophobic leucine residue.
Such a substitution can increase SDS-PAGE mobility of a 20 kDa protein
by 3% (W. W. deJong, Biochem. Biophys. Res. Commun. 82:532, 1978), probably
because leucine binds more tightly to SDS. I suggest that such an amino
acid replacement in C-zein might cause the modified molecule to move faster
by SDS-PAGE, without changing molecular mass. Increased hydrophobicity
of the modified C-zein would, however, cause it to bind more tightly to
the RP-HPLC column and thus elute later.
to the MNL 64 On-Line Index
Return to the Maize Newsletter Index
Return to the Maize Genome Database Page