Importance and General Function

The signal-mediating function of Ca is performed as a Ca Tcahnodulin complex in many signaling pathways. Ca /catmodulin can bind specifically to effector proteins and modulate their activity. In first place as effector proteins of Ca Tcahnodulin are the /calmodulin protein kinases (CaM kinases) (review Braun and Schuhnan, 1995). The CaM kinases are widespread and are found in practically all cells of mam- 

A rough categorization of the CaM kinases differentiates between specialized CaM kinases and multifunctional kinases. 

An example of a specialized CaM kinase is myosin light chain kinase (MLCK), the primary fimction of which is to phosphorylate the light chain of myosin and thus to control the contraction of smooth musculature. 

The multifimctional CaM kinases are collectively referred to as CaM kinases of type II, whereby further subtypes a, p, y and 6 are differentiated. The a and P subtypes of CaM kinase II only occur in the brain whereas the other subtypes are also found in other organs. The multifunctional CaM kinases regulate many processes (see Table 7.1) such as glycogen metabolism, activity of transcription factors, microfilament formation, synaptic release of neurotransmitters from storage vesicles, biosynthesis of neurotransmitters and many more. An important cellular function is assigned to CaM kinase II in brain, where it makes up 0.25 % of the total protein. 

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