| 초록 |
We have investigated the correlation between amino acid sequence and pH-induced conformational change of fusion protein of influenza hemagglutinin using the finite Poisson-Boltzmann method and an atomistic molecular dynamic simulation. Two parts of the fusion protein are generated as independent helices: One is the fusion peptide (residue 1~20), which forms a helix and is inserted to a target membrane under the condition of low pH. The other part (residue 56~75) also forms a helix under the condition of low pH, which leads to a dramatic change of hemagglutinin that makes the fusion peptide reach a target membrane. It is realized that the helical structure of the fusion peptide has a common feature of amphipathic helix and shows a clear helix-coil transition upon pH-decrease. On the other hand, the sequence distribution of the second part is not periodic to form an amphipathic helix as compared to the fusion peptide. In addition, the calculation for the model helix of the second part shows that the helix structure is stable in the entire range of pH investigated in the present study and the free energy of helix increases slightly upon pH-decrease. It is inferred from the calculation that the pH-dependent conformational change of the second part needs additional interactions such as the formation of trimer structure and the interaction with lipid bilayer. The effect of additions of other hemagglutinin and lipid bilayer on the pH-dependent properties is discussed in detail.
|
