Biomimetic design of affinity peptide ligand for capsomere of virus-like particle.

Virus-like particle (VLP) of murine polyomavirus (MPV) is a T = 7d icosahedral capsid that self-assembles from 72 capsomeres (Caps), each of which is a pentamer of major coat protein VP1. VLP has great potential in vaccinology, gene therapy, drug delivery, and materials science. However, its application is hindered by high cost downstream processes, leading to an urgent demand of a highly efficient affinity ligand for the separation and purification of Cap by affinity chromatography. Herein a biomimetic design strategy of an affinity peptide ligand of Cap has been developed on the basis of the binding structure of the C-terminus of minor coat protein (VP2-C) on the inner surface of Cap. The molecular interactions between VP2-C and Cap were first examined using all-atom molecular dynamics (MD) simulations coupled with the molecular mechanics/Poisson-Boltzmann surface area (MM/PBSA) method, where V283, P285, D286, W287, L289, and Y296 of VP2-C were identified as the hot spots. An affinity peptide library (DWXLXLXY, X denotes arbitrary amino acids except cysteine) was then constructed for virtual screening sequently by docking with AUTODOCK VINA, binding structure comparison, and final docking with ROSETTA FlexPepDock. Ten peptide candidates were selected and further confirmed by MD simulations and MM/PBSA, where DWDLRLLY was found to have the highest affinity to Cap. In DWDLRLLY, six residues are favorable for the binding, including W2, L4, L6 and Y8 inheriting from VP2-C, and R5 and L7 selected in the virtual screening. This confirms the high efficiency and accuracy of the biomimetic design strategy. DWDLRLLY was then experimentally validated by a one-step purification of Cap from crude cell lysate using affinity chromatography with the octapeptide immobilized on Sepharose gel. The purified Caps were observed to self-assemble into VLP with consistent structure of authentic MPV.