The β subunit of human Ca2+/calmodulin-dependent protein kinase II (β CaMKII) was identified by searching through an expressed sequence tag database and rapid amplification of cDNA 5′-ends and was assigned to chromosome 7. Reverse transcription-polymerase chain reaction and sequencing analysis identified at least five alternative splicing variants of β CaMKII (β, β6, βe, β′e, and β7) in brain and two of them (β6 and β7) were first detected in any species. When expressed in HEK 293 cells, the Ca2+/calmodulin-dependent kinase activity of β7, the shortest variant, was much lower than that of either β (the longest one) or βe (the medium one), suggesting possible regulation of β CaMKII activity by alternative splicing.
