Changes in isoelectric point of variant vitamin D-binding protein (GC) by oxidation of substituted cystein (SH group)

Abstract

This study was made to explore the cause of appearance of unusual variant bands of vitamin D-binding protein (group-specific component, GC). Both GC 1A2 and GC 1A3 have two main bands and two minor bands, and both variants were characterized by having cystein instead of arginine at the codon 429. The minor bands disappeared by keeping them at 37°C, or adding CuSO₄ or DTT to them. The results indicated that the characteristic main bands of GC 1A2 and GC 1A3 are derived from the oxidation of cystein (SH group) which corresponds to cystein at the codon 429.