Vitellogenin Ab structure of the amazonian Arapaima gigas.

The vitellogenin is composed by polypeptides that are precursors of egg yolk proteins that provides embryo and larvae nutrition. The mRNA encoding for vitellogenin Ab (Vtg-Ab; 4,536 bp long and 1,512 amino acids) were obtained by RNA-Seq library sequencing of pirarucu gonads. The Vtg-Ab sequences had high homology with Vtgs of other three teleosts species of the order Osteoglossiformes. The transcript of ovarian Vtg was identified based on structural criteria, and so we classify the Vtg of pirarucu as Vtg-Ab due to the truncated or shortened phosvitin (N-terminal end) and phosvitinless domain (C-terminal end). The Vtg-Ab of pirarucu present two major deletions with 133 amino acids in the Lipovitellin I domain and 89 amino acids in the truncated or shortened Phosvitin domain, both located in the N-terminal end region. The three-dimensional (3-D) structure Vtg-Ab protein shows the presence of a typical 4α-helices bundle protein that runs in anti-parallel. In general, the characterization of Vtg-Ab may be the useful elucidation of the hormonal regulation of vitellogenesis and improve the production of pirarucu for broodstock management in aquaculture and preparation of Vtg antibody production (species-specific) for sex identification.