Fig. 2.
Role of activating region strength on the phosphorylation of an attached substrate. Srb10/11 complex was mixed with 0.1 nmol of the indicated Gst-fusion proteins. Lane 1 contains a Gst-Gal4 (840–874) control peptide, which is not attached to a CTD3 substrate. Lanes 2–7 contain Gst-CTD3 fused to five peptides, two of which are deletion derivatives of Gal4 and the third of which bears F869A, a point mutation in the activating region. This point mutation decreases the activating function of Gal4 (840–881) by 3- to 4-fold (16, 17). The sequence of the fifth peptide, which has no activating region, is (YSPTSPS)3-GVTWTKLRIT-RLESLQGCLI-PLQWMMYITI-YSMMKIPNRI-PGNSS.