Bs. Yan et al., SELF-ASSOCIATION OF THE C-TERMINAL DOMAIN OF THE HEPATITIS-C VIRUS CORE PROTEIN, European journal of biochemistry, 258(1), 1998, pp. 100-106
The N-terminal region of the hepatitis-C virus (HCV) core protein is r
ich in basic residues, while the C-terminal end of the protein compris
es of a stretch of hydrophobic amino acids. Between these two extremes
is an amphipathic region with two predicted a-helical segments. This
region embodies Leu or hydrophobic residues in positions of heptad rep
eats and is possibly capable of self-association. To investigate this
possibility, the core sequence was divided into two fragments and expr
essed separately as recombinant proteins. Recombinant proteins with th
e N-terminal fragment remained as monomers even at high concentrations
in SDS/PAGE. Recombinant protein with the C-terminal fragment appeare
d largely monomeric on denaturing gels but some oligomers were also de
tected. Furthermore, proline mutations in either one of the predicted
a helices adversely affected the observed oligomerization. The self-as
sociation capacity of the core protein C-terminal region was further s
upported by results from a yeast two-hybrid system. To affirm our conc
lusion, a peptide covering the heptad repeats and the predicted a heli
ces was synthesized. Data from mass spectrometry and gel-filtration ch
romatography concluded that this peptide readily self-associated into
the homodimer. Therefore, our results suggest that the oligomerization
motifs of the HCV core protein may not be limited to the previously s
uggested N-terminal region.