Serine/threonine-protein kinase (PubMed:18390597, PubMed:20346955). Key component in the assembly and functioning of 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 (By similarity). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts (via C-terminus) with myosin. Interacts with actin. Localizes throughout the I-band except for dense bodies and in the outer edge of the A-band (PubMed:20346955). In embryo, co-localizes with lamin lmn-1 at the nuclear membrane. The localization to the nuclear envelope is lmn-1-dependent(PubMed:16410549). Expression is restricted to body wall, enteric and vulval muscles. Expression begins at 2.5-fold stage and continues throughout adulthood. The PEVK region may serve as an entropic spring to bear the passive tension of the sarcomere. The BLUE region may serve as a force and thermal sensors. The autoinhibitory domain may interact with the kinase catalytic core thereby preventing its activation. Produced by alternative splicing of isoform g. Produced by alternative splicing of isoform g. Produced by alternative splicing of isoform g. Produced by alternative splicing of isoform g. Produced by alternative splicing of isoform g. Produced by alternative splicing of isoform g. Produced by alternative promoter usage. Produced by alternative promoter usage and alternative splicing of isoform 301kDa_1. Belongs to the protein kinase superfamily. CAMK Ser/Thr protein kinase family.