Cross-linking of the UUKV-N protein. N protein containing COS-7 cell lysates were treated with 0.1 or 0.5 mM of cross-linking reagent (BS3), and resolved by 10% SDS-PAGE under denaturing conditions. An immunoblot shows that omitting BS3, the majority of the full-length UUKV-N protein migrated as 25 kDa monomeric form (lane 1). Addition of BS3 decreased the amount of the monomeric form, while the amount of dimeric and multimeric forms were simultaneously increasing (lanes 2 and 3). In mock-transfected samples no N protein was detected (lanes 4 to 6).