The type I receptor for T
The type I receptor for TGF-beta functions as this kind of enzyme, exposing the nuclear localization signal on R-SMAD. A family of these enzymes dimerizes and activates STAT transcription factors. Many proteins interact with these enzymes with the help of SH2 domains. ERK 1 and 2 are activated by a three- tiered system of these enzymes in the pathway named after their (*) MAP variety. These enzymes can be classified as those that act on serine/threonine residues, and those that act on tyrosines. Cyclins regulate the cell cycle by interacting with the cyclin-dependent type of these enzymes, which perform the opposite function as phosphatases. For 10 points, name these enzymes that add a phosphate group to a target protein.