Protein kinase C and annexins: unusual calcium response elements in the cell.
Protein kinase C and the annexins appear to share some unusual and potentially important membrane- and calcium-binding properties. While these proteins are calcium response elements, they are not calcium-binding proteins in the formal sense; at intracellular calcium concentrations, they only bind significant amounts of calcium when membranes or other suitable surfaces are present. The number of calcium ions bound per protein is large (> 8) and this stoichiometry, at the protein-membrane interface, may provide the large number of contact points needed for the very high-affinity interaction that is observed. The further ability of annexins and PKC to form structures with properties of integral membrane proteins may be important to provide a type of long-term cell signalling that produces a constitutively active kinase or ion channel activity. Selectivity for phospholipids in bilayer form is modest with respect to the acidic phospholipids but there is a surprising preference for phosphatidylethanolamine as the neutral phospholipid matrix. Along with other unusual properties, these proteins offer the potential for unique types of cell regulation events.
Department of Biochemistry, University of Minnesota, St Paul 55108.
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MD
Bazzi
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GL
Nelsestuen
D000818:Animals; D017302:Annexins / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D011493:Protein Kinase C / Q000378:metabolism*; D015398:Signal Transduction
D017302:Annexins; D011493:Protein Kinase C; D002118:Calcium