Poxvirus mRNA cap methyltransferase. Bypass of the requirement for the stimulatory subunit by mutations in the catalytic subunit and evidence for intersubunit allostery. Academic Article uri icon

Overview

abstract

  • The guanine-N7 methyltransferase domain of vaccinia virus mRNA capping enzyme is a heterodimer composed of a catalytic subunit vD1-(540-844) and a stimulatory subunit vD12. The poxvirus enzyme can function in vivo in Saccharomyces cerevisiae in lieu of the essential cellular cap methyltransferase Abd1. Coexpression of both poxvirus subunits is required to complement the growth of abd1delta cells. We performed a genetic screen for mutations in the catalytic subunit that bypassed the requirement for the stimulatory subunit in vivo. We thereby identified missense changes in vicinal residues Tyr-752 (to Ser, Cys, or His) and Asn-753 (to Ile), which are located in the cap guanine-binding pocket. Biochemical experiments illuminated a mechanism of intersubunit allostery, whereby the vD12 subunit enhances the affinity of the catalytic subunit for AdoMet and the cap guanine methyl acceptor by 6- and 14-fold, respectively, and increases kcat by a factor of 4. The bypass mutations elicited gains of function in both vD12-independent and vD12-dependent catalysis of cap methylation in vitro when compared with wild-type vD1-(540-844). These results highlight the power of yeast as a surrogate model for the genetic analysis of interacting poxvirus proteins and demonstrate that the activity of an RNA processing enzyme can be augmented through selection and protein engineering.

publication date

  • May 16, 2006

Research

keywords

  • Methyltransferases
  • Mutation
  • Poxviridae
  • RNA, Messenger

Identity

Scopus Document Identifier

  • 33745868309

Digital Object Identifier (DOI)

  • 10.1074/jbc.M602867200

PubMed ID

  • 16707499

Additional Document Info

volume

  • 281

issue

  • 28