Molecular characterization of vitellin from the ovaries of the white shrimp Penaeus ( Litopenaeus) vannamei

Abstract

Vitellin (Vt) was purified from ovary extracts of mature females of the white shrimp Penaeus vannamei using Sepharose CL-4B and Q-Sepharose columns. Native Vt had an apparent molecular weight of 388 kDa as detected in Native-PAGE, bound the lipophilic dye Oil Red O and had a total lipid content of ∼43.8%. Under reducing and denaturing conditions (SDS-PAGE), Vt is composed of three major subunits of 87, 78 and 46 kDa, although minor bands of 65, 61 and 31 kDa are also detected. The 87- and 78-kDa polypeptides were strongly recognized by Penaeus semisulcatus anti-Vt polyclonal and Penaeus monodon anti-Vt monoclonal antibodies. Furthermore, the N-terminal amino acid sequence of the 78-kDa polypeptide is very similar to Penaeus japonicus vitellogenin (Vg) and P. semisulcatus Vt, with an identity of 76%. Circular dichroism indicates that the β-helix content of Vt is 25% while β-sheets correspond to 37 and 14% of unordered secondary structure. These values are similar to insect microvitellogenin. Vt has an emission fluorescence maximum at 329 nm, comparable to the shrimp high-density lipoprotein/beta-glucan binding protein (HDL/BGBP).