Signal transduction calcium binding proteins

Small ubiquitous calcium-binding protein. Calmodulin binds and regulates the activity of many protein targets involved in cellular signal transduction pathways mediated by calcium. Calmodulin is ranked among the most conserved proteins and plays a key role in many cellular processes. 

Unfortunately, at the present time the physiological function of the majority of calcium binding proteins is unknown, and before the complexity of the calcium messenger system can be completely elucidated, the function of these proteins must be clarified. Accordingly, the purpose of the review is to briefly document the various cellular calcium binding proteins and where possible discuss the role of these proteins in the signal transduction process. Since our knowledge of the role of cal-... 

A calcium binding protein could play a role in transduction of the calcium signal in one or more of three possible ways. First, it could serve as a calcium buffer protein for instance in response to cellular activation it could release bound calcium... 

DEAE-Sepharose in low calcium. In addition to these relatively soluble calcium-binding proteins, other less soluble EF hand proteins (eg. GCAP) can be purified by relatively simple procedures. Such isolation procedures will be of increasing importance for studying signal transduction pathways that involve calcium. 

In the PIP2-Ca signal transduction system, the signal is transferred from the epinephrine receptor to membrane-bound phospholipase C by G proteins. Phospholipase C hydrolyzes PIP2 to form diacylglycerol (DAG) and inositol trisphos-phate (IP3). IP3 stimulates the release of Ca from the endoplasmic reticulum. Ca and DAG activate protein kinase C. The amount of calcium bound to one of the calcium-binding proteins, calmodulin, is also increased. 

Fig. 5 Proposed signal transduction mechanisms that stimulate the pheromone biosynthetic pathway in Helicoverpa zea and Bombyx mori. It is proposed that PBAN binds to a G protein-coupled receptor present in the cell membrane that upon PBAN binding will induce a receptor-activated calcium channel to open causing an influx of extracellular calcium. This calcium binds to calmodulin and in the case of B. mori will directly stimulate a phosphatase that will dephosphorylate and activate a reductase in the biosynthetic pathway. In H. zea the calcium-calmodulin will activate adenylate cyclase to produce cAMP that will then act through kinases and/or phosphatases to stimulate acetyl-CoA carboxylase in the biosynthetic pathway...

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