Calmodulin mediates the control of a large number of enzymes, ion channels, aquaporins and other proteins through calcium-binding. Among the enzymes to be stimulated by the calmodulin-calcium complex are a number of protein kinases and phosphatases. Together with CCP110 and centrin, is involved in a genetic pathway that regulates the centrosome cycle and progression through cytokinesis. Mediates calcium-dependent inactivation of CACNA1C. Positively regulates calcium-activated potassium channel activity of KCNN2. Interacts with CEP97, CCP110, MYO1C, TTN/titin and SRY. Interacts with MYO10. Interacts with RRAD (By similarity). Interacts with USP6; the interaction is calcium dependent (By similarity). Interacts with CDK5RAP2. Interacts with SCN5A (By similarity). Interacts with FCHO1. Interacts with MIP in a 1:2 stoichiometry; the interaction with the cytoplasmic domains from two MIP subunits promotes MIP water channel closure. Interacts with ORAI1; this may play a role in the regulation of ORAI1-mediated calcium transport (By similarity). Interacts with RYR1 (PubMed:18650434). Interacts with MYO5A (By similarity). Interacts with IQCF1 (PubMed:25380116). Interacts with SYT7 (PubMed:24569478). Interacts with CEACAM1 (via cytoplasmic domain); this interaction is in a calcium dependent manner and reduces homophilic cell adhesion through dissociation of dimer (By similarity). Interacts with RYR2; regulates RYR2 calcium-release channel activity (PubMed:18650434). Interacts with PCP4; regulates calmodulin calcium-binding (By similarity). Interacts with the heterotetrameric KCNQ2 and KCNQ3 channel; the interaction is calcium-independent, constitutive and participates in the proper assembly of a functional heterotetrameric M channel (By similarity). Distributed throughout the cell during interphase, but during mitosis becomes dramatically localized to the spindle poles and the spindle microtubules. Ubiquitination results in a strongly decreased activity. Phosphorylation results in a decreased activity. This protein has four functional calcium-binding sites. Belongs to the calmodulin family.