Structural explanation for the role of Mn^2+ in the activity of Φ6 RNA-dependent RNA polymerase

Journal article

The biological role of manganese (MN^2+) has been a long-standing puzzle, since at low concentrations it activates several polymerases whilst at higher concentrations it inhibits. Viral RNA polymerases possess a common architecture, reminiscent of a closed right hand. The RNA-dependent RNA polymerase (RdRp) of bacteriophage Φ6 is one of the best understood examples of this important class of polymerases. We have probed the role of MN^2+ by biochemical, biophysical and structural analyses of the wild-type enzyme and of a mutant form with an altered Mn^2+ -binding site (E491 to Q). The E491Q mutant has much reduced affinity for Mn^2+, reduced RNA binding and a compromised elongation rate. Loss of Mn^2+ binding structurally stabilizes the enzyme. These data and a re-examination of the structures of other viral RNA polymerases clarify the role of manganese in the activation of polymerization: Mn^2+ coordination of a catalytic aspartate is necessary to allow the active site to properly engage with the triphosphates of the incoming NTPs. The structural flexibility caused by Mn^2+ is also important for the enzyme dynamics, explaining the requirement for manganese throughout RNA polymerization.

Authors: Poranen, M; Salgado, P; Koivunen, M; Wright, S; Bamford, D

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Oxford University Press
• Journal: Nucleic Acids Research
• Volume: 36
• Issue: 20
• Pages: 6633-6644
• Publication date: 2008-11-01
• Edition: Publisher's version
• DOI: 10.1093/nar/gkn632
• EISSN: 1362-4962
• ISSN: 0305-1048
• Language: English
• Keywords: manganese; RNA-dependent RNA polymerase (RdRp)
• Subjects: Biology; Structural genomics