Key component in the assembly and functioning of vertebrate striated muscles. By providing connections at the level of individual microfilaments, it contributes to the fine balance of forces between the two halves of the sarcomere. The size and extensibility of the cross-links are the main determinants of sarcomere extensibility properties of muscle. In non-muscle cells, seems to play a role in chromosome condensation and chromosome segregation during mitosis. Might link the lamina network to chromatin or nuclear actin, or both during interphase. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Full activation of the protein kinase domain requires both phosphorylation of Tyr-33203, preventing it from blocking the catalytic aspartate residue, and binding of Ca/CALM to the C-terminal regulatory tail of the molecule which results in ATP binding to the kinase. Interacts with MYOM1, MYOM2, tropomyosin and myosin. Interacts with actin, primarily via the PEVK domains and with MYPN. Interacts with FHL2, NEB, CRYAB, LMNA/lamin-A and LMNB/lamin-B. Interacts with TCAP/telethonin and/or ANK1 isoform Mu17/ank1.5, via the first two N-terminal immunoglobulin domains. Interacts with TRIM63, TRIM55, ANKRD1, ANKRD2, ANKRD23, and CAPN3 through several Ig domains. Interacts with NBR1 through the protein kinase domain (By similarity). Interacts with CMYA5 (By similarity). Expressed in cardiac muscle from 8 dpc and in skeletal muscle from 9 dpc. ZIS1 and ZIS5 regions contain multiple SPXR consensus sites for ERK- and CDK-like protein kinases as well as multiple SP motifs. ZIS1 could adopt a closed conformation which would block the TCAP-binding site (By similarity). The PEVK region may serve as an entropic spring of a chain of structural folds and may also be an interaction site to other myofilament proteins to form interfilament connectivity in the sarcomere. Autophosphorylated. Belongs to the protein kinase superfamily. CAMK Ser/Thr protein kinase family.