Cross-linking of poliovirus with bifunctional reagents: biochemical and immunological identification of protein neighbourhoods.

Poliovirus was treated with the homobifunctional reagents 1,5-bis (succinimidooxycarbonyloxy)pentane (BSOCOP) and dimethyl adipimidate, both reacting with epsilon-amino-groups of lysines and N-terminal amino acids, respectively. Cross-links between separate virus particles did not occur and their physical stability remained unaltered as determined by sucrose gradient centrifugation. Using BSOCOP intermolecular protein complexes of different sizes, namely 59K, 71K and 92K, were obtained. Their compositions were identified after cleavage by the relative mobilities of the proteins in SDS-PAGE and particularly by immunoblot analysis using protein-specific polyclonal antisera. The three major capsid proteins were involved in cross-linking. The 59K complex consisted of VP1-VP3, the 71K complex of VP1-VP2 and the 92K complex of VP2-VP1-VP3, reflecting neighbourhoods of the respective proteins in the icosahedral virus capsid. It is suggested that cross-linking took place between proteins in a protomer rather than between proteins of adjacent protomers, trimers or pentamers.