The present invention provides an isolated nucleic acid comprising the nucleotides set forth in the Sequence Listing as SEQ ID NO: 1. SEQ ID NO: 1 is an example of GP64-6His nucleic acid. The invention further provides polypeptides encoded by GP64-6His nucleic acids as well as the polypeptide encoded by SEQ ID NO: 2. The invention also provides liposomes comprising GP64-6His polypeptides as well as liposomes comprising GP64-6His polypeptides and biological molecules. The invention further provides a method of increasing the solubility of polypeptides comprising linking a 6His tag to a polypeptide and measuring the solubility of the 6His-tagged polypeptide, whereby an increase in solubility of the 6His-tagged polypeptide can be detected. The invention also provides a method of solubilizing a viral fusion polypeptide comprising linking a 6His tag to a viral fusion polypeptide. Further provided is a method of delivering a biological molecule to a cell comprising, administering the liposome comprising a GP64-6His polypeptide to a cell. This invention also provides a method of delivering a viral vaccine to a cell comprising administering the liposome comprising a GP64-6His polypeptide to a cell. Also provided is a method of delivering a DNA vaccine to a cell comprising administering the liposome comprising a GP64-6His polypeptide to a cell. Further provided is a GP64-6His polypeptide further comprising a binding site for a cell surface molecule. Also provided by this invention are chimeric proteins comprising GP64-6His.