The Purification and Structural Characterization of the Fusion Factor of Sendai Virus

Summary

The fusion factor (F) and the hemagglutinin-neuraminidase (HN) of Sendai virus have been purified by lectin affinity chromatography on a Lens culimris (LcH)-Sepharose column. Separation was achieved by sequential elution with two different detergents containing a methyl mannoside. HN was eluted with the zwitterionic detergent Empigen BB and F with the anionic detergent sodium deoxycholate. F was further purified by molecular sieving on Ultrogel AcA34 and separated into its two component chains (F₁ apparent M.W. 53,000 and F2 apparent M.W. 15,000) by molecular sieving on Sephadex G-100 after reduction of disulfide bonds. The amino terminus of F₁ was PHE-PHE-GLY-ALA-VAL-ILE-GLY-ILEILE-ALA-. This sequence shows identity at six positions with the amino terminal sequence of the small polypeptide chain (HA₂) of the influenza virus hemagglutinin. The amino terminal ten residues of F₁ and HA₂ are extremely hydrophobic and are both generated by proteolytic cleavage of an inactive precursor polypeptide. Structure and function correlations of this cleavage are discussed.