Isoform 2 may have a role in regulating the growth and differentiation of arterial smooth muscle cells. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with MTM1 (By similarity). Isoform 2 is highly expressed in differentiated arterial smooth muscle cells (ASMC) in the medial layer of the aorta. Weakly detected in brain and testis and to a lesser extent in organs rich in striated muscle or visceral smooth muscle. May be autophosphorylated. Expression is under the tight control of the locus control region (LCRs). Produced by alternative promoter usage. Belongs to the protein kinase superfamily. CAMK Ser/Thr protein kinase family.