Heterogeneity in end-terminal sugars of rabbit and rat androgen binding protein (ABP)

The interaction between rabbit and rat androgen binding protein (ABP) and rabbit serum testosterone binding globulin (TeBG) with concanavalin A (Con A) was studied using affinity chromatography on Con A-Sepharose 4 B columns. When partly purified rat ABP, equilibrated with [3H]5 alpha-dihydrotesterone [3H]DHT was applied to Con A-Sepharose columns, approximately 50% of the ABP was retained by the column, whereas the remaining was eluted with the break-through protein fraction. A similar picture was found using partly purified rabbit ABP, or crude rabbit rete testis fluid. These studies indicate that both rat and rabbit ABP are glycoproteins, showing heterogeneity in their end-terminal sugars. When partly purified rabbit TeBG was examined by Con A-Sepharose affinity chromatography, the TeBG was completely retained by the column. The different elution patterns between rabbit ABP and rabbit TeBG indicate that these proteins, although showing identical physico-chemical and immunological properties (Weddington et al. 1975a,b), possess differences in their carbohydrate content.