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Cystic fibrosis transmembrane conductance regulator; Phosphorylation site; Membrane-bound phosphatase; ATP dependence; Phosphatase
Abstract:
The cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel which is activated by protein phosphorylation and nucleoside triphosphates. We demonstrate here that fusion of the soluble catalytic subunit of cAMP-dependent protein kinase to the membrane protein bacteriorhodopsin yields a constitutively active protein kinase which activates CFTR effectively. As it is membrane-bound it is particularly useful for continuous perfusion of excised inside-out patches. We also tested the effect of a naturally membrane-bound protein kinase, cGMP-dependent protein kinase II, on CFTR. Both kinases, when continuously active, increase apparent affinity of CFTR to ATP about two-fold emphasizing the role of phosphorylation in modulating the interaction of ATP with the nucleotide binding domains.
