Vitellogenin and yolk protein processing in Bothrops jararaca (Wied), a tropical venomous snake

Abstract

The plasma vitellogenin of Bothrops jararaca is composed of two subunits. The larger subunit (160 kDa) is phosphate rich and carbohydrate poor, while the smaller (110 kDa) is highly glycosylated and less phosphorylated. As in other vertebrates, the vitellogenin of B. jararaca is synthesized in the liver under estrogen control. The newly synthesized vitellogenin molecule is a 270 kDa polypeptide. This polypeptide originates the two subunits of the plasma vitellogenin by proteolytic cleavage. In the eggs of B. jararaca six main yolk polypeptides have been detected (113, 107, 104, 72, 27.2 and 20.7 kDa). Using phosphoprotein staining we have shown that the 72 kDa polypeptide is the larger phosvitin so far described in a vertebrate egg yolk. The 107 kDa yolk polypeptide also seems to be phosphorylated, but to a lesser extent than the phosvitin. The 104 kDa vitellin originates from the larger vitellogenin subunit while the 113 kDa vitellin originates from the smaller vitellogenin subunit. Based on these results we propose a general scheme for vitellogenin and vitellin processing in B. jararaca.