title: Oligomerization of hantaviral nucleocapsid protein: charged residues in the N-terminal coiled-coil domain contribute to intermolecular interactions.
abstract: The nucleocapsid (N) protein of hantaviruses (family Bunyaviridae) is the most abundant component of the virion; it encapsidates genomic RNA segments and participates in viral genome transcription and replication, as well as in virus assembly. During RNA encapsidation, the N protein forms intermediate trimers and then oligomers via 'head-to-head, tail-to-tail' interactions. In previous work, using Tula hantavirus (TULV) N protein as a model, it was demonstrated that an intact coiled-coil structure of the N terminus is crucial for the oligomerization capacity of the N protein and that the hydrophobic 'a' residues from the second alpha-helix are especially important. Here, the importance of charged amino acid residues located within the coiled-coil for trimer formation and oligomerization was analysed. To predict the interacting surfaces of the monomers, the previous in silico model of TULV coiled-coils was first upgraded, taking advantage of the recently published crystal structure of the N-terminal coiled-coil of the Sin Nombre virus N protein. The results obtained using a mammalian two-hybrid assay suggested that conserved, charged amino acid residues within the coiled-coil make a substantial contribution to N protein oligomerization. This contribution probably involves (i) the formation of interacting surfaces of the N monomers (residues D35 and D38, located at the tip of the coiled-coil loop, and R63 appear particularly important) and (ii) stabilization of the coiled-coil via intramolecular ionic bridging (with E55 as a key player). It is hypothesized that the tips of the coiled-coils are the first to come into direct contact and thus to initiate tight packing of the three structures.
authors.affiliation: Department of Virology, Haartman Institute, PO Box 21, FIN-00014 University of Helsinki, Finland.
authors.forename: Agne
authors.initials: A
authors.lastname: Alminaite
authors.affiliation: Department of Biochemistry and Pharmacy, Åbo Akademi University, Turku, Finland.
authors.forename: Vera
authors.initials: V
authors.lastname: Backström
authors.affiliation: Department of Virology, Haartman Institute, PO Box 21, FIN-00014 University of Helsinki, Finland.
authors.forename: Antti
authors.initials: A
authors.lastname: Vaheri
authors.affiliation: Department of Virology, Haartman Institute, PO Box 21, FIN-00014 University of Helsinki, Finland.
authors.forename: Alexander
authors.initials: A
authors.lastname: Plyusnin