Detection of HBV C Protein Phosphorylation in the Cell

Abstract

Among the seven serines and one threonine in the carboxyl-terminus of HBV C protein, all but one (serine 183) appear in the context of RxxS/T consensus phosphoacceptor motifs and also overlap with other consensus motifs, such as S/TP, RS, SPRRR, RRRS/T, or RRxS/T, suggesting that various cellular kinases phosphorylate these residues. To determine whether threonine and/or serine (serines 157, 164, 170, 172, 178, and 180, and threonine 162, adw subtype) of HBV C protein are indeed phosphoacceptor residues in cells, Huh7 were transfected with a series of C-protein-expressing mutants, labeled with 32P-orthophosphate for 14 h, and then lysed. The 32Pi-labeled lysates were immunoprecipitated with anti-HBc antibody, and the 32Pi-labeled immunoprecipitated C proteins were detected by autoradiography.