The HBx protein mutation among different HBV genotypes

Objective To study the significance of HBx protein mutation among the different HBV genotypes.Methods Complete HBx protein mutation sequences were identified and analyzed with different HBV genotypes using Clustalw 2.0 software.Results The homology was 73%～100% among HBx protein amino acid sequences and different HBV genotypes.The homologies of HBx protein sequences were 87%～99%, 88%～96%, 87%～99%, 86%～96%, 96%～98%, and 99%～100% in HBV genotype B, C, D, F, A, and H, respectively.The fifth and twelfth amino acid in A region of HBx protein (1～20aa) were highly varied and amino acid of the other region were highly conserved.The amino acid in the B region of HBx protein was highly varied and it was randomly varied even within HBx protein sequence of the same HBV genotype.In the C region (58～84aa) amino acids were more conserved, in addition to the sixtieth amino acid in the three H genotype HBx protein A (ALA) .The rest were V (Valine) and the remaining positions were rarely mutated.Variations of amino acids (85～119aa) in HBx protein D region were larger and random.The various locations of HBx protein E region (120～140aa) were amino acid 130/131, and amino acids of the remaining location were less mutated.The 130/131 amino acid mutation of HBx protein in different genotypes was not consistent.In HBx protein F region, the amino acids 141～154aa and 150～154aa were more conserved.There was no variation between different HBV genotypes and HBx protein whereas the remaining amino acids showed larger variation.Conclusion The homology of HBx protein amino acid sequence between different HBV genotypes is lower than the homology found within the same genotype.Highly varied amino acid loci exist in the more conserved areas of HBx protein.