Interaction of peptides with sequences from the Newcastle disease virus fusion protein heptad repeat regions

Typical of many viral fusion proteins, the sequence of the Newcastle diseas e virus (NDV) fusion protein has several heptad repeat regions. One, HR1, i s located just carboxyl terminal to the fusion peptide, while the other, HR 2, is located adjacent to the transmembrane domain. The structure and funct ion of a synthetic peptide with a sequence from the region of tbe NDV HR1 r egion (amino acids 150 to 173) were characterized. The peptide inhibited fu sion with a half-maximal concentration of approximately 2 mu M; however, in hibition was observed only if the peptide was added prior to protease activ ation of the fusion protein. This inhibition was virus specific since the p eptide had minimal effect on fusion directed by the Sendai virus glycoprote ins. To explore the mechanism of action, the potential HR1 peptide interact ion with a previously characterized fusion inhibitory peptide with a sequen ce from the HR2 domain (J. K. Young, R. P. Hicks, G. E. Wright, and T. G. M orrison, Virology 238:291-304, 1997) was characterized. The results demonst rated an interaction between the two peptides both functionally and directl y. First, while the individual peptides each inhibit fusion, equimolar mixt ures of the two peptides had minimal effect on fusion, suggesting that the two peptides form a complex preventing their interaction with a target prot ein. Second, an HR2 peptide covalently linked with biotin was found to bind specifically to HR1 peptide in a Western blot. The structure of the HR1 pe ptide was analyzed by nuclear magnetic resonance spectroscopy and found to be an alpha helix.