Structure of transmembrane subunits gp47 of the foamy virus envelope glycoproteins

The successful foamy viruses (FVs) infection includes at least two essential events, attachment to the cell surface and fusion of the viral envelope with the cell membrane. For the FVs, membrane fusion between virus and cell is mediated by envelope glycoprotein (Env) transmembrane (TM) subunit gp47. Compared with other retroviruses, FV TM subunit shares a similar but not identical structural characteristic. This paper focuses on in sillico analyses of all 15 available FV TM subunits gp47 based on their amino acid sequences. The hydrophobicity analysis revealed that the 15 FVs gp47 had two prominent hydrophobic regions, the N-terminal fusion peptide (FP) and the C-terminal region, which included a membrane-spanning domain (MSD) and a membrane proximal ectodomain region (MPER). In most FVs gp47, two heptad repeats, the coiled coils characterized by repetition of 7-amino acid-motif, were found to be correspondently located downstream of FP (named "N-HR") and the upstream of MPER (named "C-HR"). Furthermore, the solvent accessibility and secondary structure were predicted for all FVs gp47. These observations suggested that FVs gp47 possessed several fusion domains, which were necessary in the process of lipid membrane fusion between FVs and the target cells.