Crystal structures of RNA 3'-terminal phosphate cyclase and its complexes with Mg2++ATP, ATP or Mn2+

Abstract

RNA 3′-terminal phosphate cyclase (Rtc) is an enzyme related to RNA splicing, in which the 3′-terminal hydroxyl group of a truncated RNA is converted to the 2′,3′-cyclic phosphate that is required prior to RNA ligation. This reaction may occur in the following two steps: (i) Rtc + ATP → Rtc-AMP + Ppi and (ii) RNA-N3' + Rtc-AMP → RNA-N>p + Rtc + AMP. In order to establish the reaction mechanism, Rtc of Sulfolobus tokodaii, overexpressed in E. coli, was crystallized in the following states, Rtc, Rtc-AMP, Rtc:AMP, Rtc:ATP and Rtc:Mn, and their crystal structures have been determined at 2.25, 2.25, 2.9, 2.4 and 3.2 Å resolutions, respectively. Based on these structures, a possible reaction mechanism has been proposed.