National Center for
4GZK: Structure and Interactions of the RNA-dependent RNA Polymerase From Bacteriophage Phi12
Proteins (2013) 81 p.1479-1484
We have determined the structure of P2, the self-priming RdRp from cystovirus phi12 in two crystal forms (A, B) at resolutions of 1.7 A and 2.1 A. Form A contains Mg(2+) bound at a site that deviates from the canonical noncatalytic position seen in form B. These structures provide insight into the temperature sensitivity of a ts-mutant. However, the tunnel through which template ssRNA accesses the active site is partially occluded by a flexible loop; this feature, along with suboptimal positioning of other structural elements that prevent the formation of a stable initiation complex, indicate an inactive conformation in crystallo.