Positively Charged Amino Acid Residues of VP1 Capsid Protein of Human Polyomavirus BK Influence on the Formation of Virus-like Particles Generated by Recombinant Baculoviruses
Abstract: VP1 is the major structural protein of the human polyomavirus BK and can be used for the generation of virus-like particles (VLP) in vitro by using recombinant baculoviruses. To determine the role of positively charged residues R-281, R-285, K-288, R-290, R-292, K-293, R-294, and K297 at the C terminal of VP1 in VLP formation and DNA binding, we separately changed the residue to alanine, and expressed VP1 protein. The results showed that substitution of K-288, R-290, R-292, K-293, R-294, and K297 with alaninecan still form VLP, but compared with wild type there were some differences in releasing VLP into culture medium and binding between major capsid proteins and cellular DNA . Interestingly,after substituting R-281 and R-285 with alanine, a few VLP in cell but no VLP were detected respectively. This study provides evidence that positively charged residues R-281 and R-285 are necessary to form VLP and the others can influence the binding between major capsid proteins and cellular DNA.