Purification of a circulatory riboflavin carrier protein from pregnant bonnet monkey (M. radiata): comparison with chicken egg vitamin carrier

A specific protein exhibiting immunological cross-reactivity with chicken egg-white riboflavin carrier protein was detected by radioimmunoassay in the pregnancy sera of bonnet monkeys (Macaca radiata). Tiffs protein, which is capable of binding [14C]riboflavin, was purified by gel filtration on Sephacryl 8-300, fast protein liquid chromatography on a Mono Q anion exchanger and chromatofocusing on Mono P columns. The isolated primate carrier protein was similar to its avian counterpart in terms of physicochemicai characteristics, such as isoelectric point (pl < 4), electrophoretic mobility, molecular weight (approx. 36 000) and iigand binding. These findings may account for the extensive immunological cross-reactivity observed between the two proteins and suggest that the two vitamin carriers may have similar function in terms of embryonic vitamin nutrition