The Ca2+/calmodulin-dependent protein kinases (CaMKs) comprise a structurally related subfamily of serine/threonine kinases. CaMKI Beta (Ca2+/calmodulin-dependent protein kinase type 1B), also known as PNCK (pregnancy up-regulated non-ubiquitously expressed CaM kinase) or BSTK3, is a 343 amino acid protein that localizes to both the nucleus and the cytoplasm and contains one protein kinase domain. Existing as multiple alternatively spliced isoforms, CaMKI Beta functions to catalyze the ATP-dependent phosphorylation of CaMKI, an event that activates CaMKI activity and may be important for Ca2+-triggered signaling cascades within the cell. The gene encoding CaMKI Beta maps to human chromosome X, which contains nearly 153 million base pairs and houses over 1,000 genes.