Detection of p110 as a gRNA-binding protein. (A) 10 ml of a Superose-6 gel filtration fraction of a L. tarentolae TS mitochondrial extract containing the peak of TUTase activity was incubated with [32P]ATP-labeled gND7-II gRNA. The sample was electrophoresed in a 4-16% native acrylamide gradient gel, which was exposed wet. The lane was excised and UV cross-linked and RNaseA-digested, and the labeled products separated in an SDS-acrylamide gel. The dried gel was exposed for Phosphorimager analysis. (B) Aliquots (10 *l) of TS mitochondrial extract were incubated 40 min at 27°C with [32P]UTP or with [32P]ATP uniformly labeled synthetic gRNA (gND7-II). The material was then subjected to UV cross-linking and RNaseA-digestion and the products separated in an SDS-acrylamide gel. The gel was vacuum-dried and exposed to film. Molecular weight markers are indicated (kD).