Structural features of the scaffold interaction domain at the N terminus of the major capsid protein (VP5) of herpes simplex virus type 1

Eugene Huang, Edward M. Perkins, Prashant Desai

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Protein-protein interactions drive the assembly of the herpes simplex virus type 1 capsid. A key interaction occurs between the C terminus of the scaffold protein and the N terminus of the major capsid protein (VP5). Results from alanine-scanning mutagenesis of hydrophobic residues in the N terminus of VP5 revealed seven residues (127, L35, F39, L58, L65, L67, and L71) that reside in two predicted alpha helices (helix 122-42 and helix 2 58-72) that are important for this bimolecular interaction. The goal of the present study was to further characterize the VP5 scaffold interaction domain (SID). Amino acids at the seven positions were replaced with L, M, V or P (127); I, M, V, or P (L35, L58, L65, L67, and L71); and H, W, Y, or L (F39). Replacement with a hydrophobic side chain did not affect the interaction with scaffold protein in yeast cells or the ability of a virus specifying the mutation from replicating in cells. The mutation to the proline side chain abolished the interaction in all cases and was lethal for virus replication. Mutant viruses with proline substitutions in helix 122-42 at positions 27 and 35 assembled large open capsid shells that did not attain closure. Proline substitutions in helix 258-72 at either position 59, 65, or 67 abolished the accumulation of VP5 protein, and, at 58 and 71, although VP5 did accumulate, capsid shells were not assembled. Thus, the second SID, SID2, is highly structured, and this alpha helix (helix 258-72) is likely involved in capsomere-capsomere interactions during shell accretion. Conserved glycine G59 in helix 258-72 was also mutated. G59 may act as a flexible "hinge" in helix 258-72 because decreasing the movement of this side chain by replacement with valine impaired capsid assembly. Thus, the N terminus of VP5 and the alpha helices embedded in this domain, as in the capsid shell proteins of some double-stranded DNA phages, are a key regulator of shell accretion and stabilization.

Original languageEnglish (US)
Pages (from-to)9396-9407
Number of pages12
JournalJournal of virology
Issue number17
StatePublished - Sep 2007

ASJC Scopus subject areas

  • Microbiology
  • Immunology
  • Insect Science
  • Virology


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