In silico prediction of the binding structure between vitellogenin and vitellogenin receptor of Haemaphysalis longicornis.

Abstract

Vitellogenin (Vtg) and its receptor (VtgR)-essential for yolk deposition and transovarial pathogen transmission in ticks-are compelling targets for antibody-based intervention. To investigate their interaction in the tick Haemaphysalic longicornis, we employed AlphaFold2 to model the β-barrel domain of the midgut-synthesized paralog HlVtg1 and the first three ligand-binding repeats (LBR1-3) of HlVtgR. Subsequent protein-protein docking in Molecular Operating Environment (MOE) revealed a recurrent binding interface centered on HlVtg1's Glu87, which formed persistent electrostatic interactions with LBR1-3 across top-ranking poses. Our results support a "monomeric engagement" model, where a single HlVtg1 monomer simultaneously engages all three low-density lipoprotein receptor class-A (LDLRA) domains of HlVtgR. This mechanism contrasts with the classical dimeric model and challenges prior inferences about stoichiometry and symmetry of binding sites. The predicted contact residues defined here may serve as a useful basis for evaluating candidate epitopes for interventions aimed at disrupting oocyte maturation and transovarial transmission of pathogens in H. longicornis.