title: Circular dichroism analysis of ligand-induced conformational changes in protein kinase C. Mechanism of translocation of the enzyme from the cytosol to the membranes and its implications.
abstract: The structural changes following the binding to protein kinase C (PKC) of activators that promote its translocation to lipid environments were studied by far-u.v. c.d. and intrinsic fluorescence measurements of the protein. In the absence of activators, PKC contained 40% alpha-helix, with an average size of 13 amino acids per alpha-helix segment, and 12% beta-structure as deduced from c.d. spectral analysis while fitting a set of model proteins of known structure. Ligands that promote translocation and activation of the enzyme, such as Ca2+ ions and phorbol esters, produced drastic changes in the c.d. spectra which may be interpreted as a reduction in the average number of consecutive amino acids in the alpha-helix. Most of the total alpha-helix structure was conserved and an increase in beta-structure was produced by active phorbol esters. These activators differentially affected the fluorescence of PKC: phorbol esters shifted the emission maximum to the red, whereas Ca2+ produced a marked decrease in the intensity of the fluorescence emission, suggesting in both cases that tryptophan residues were exposed to increased polar environments after binding of the ligands.
authors.affiliation: Instituto de Bioquímica, Facultad de Farmacia, Universidad Complutense, Madrid, Spain.
authors.forename: L
authors.initials: L
authors.lastname: Boscá
authors.forename: F
authors.initials: F
authors.lastname: Morán
mesh_terms: D000818:Animals; D001692:Biological Transport; D001921:Brain / Q000201:enzymology*; D002118:Calcium / Q000494:pharmacology; D002417:Cattle; D002462:Cell Membrane / Q000201:enzymology*; D002942:Circular Dichroism; D003600:Cytosol / Q000201:enzymology*; D004533:Egtazic Acid / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D011487:Protein Conformation; D011493:Protein Kinase C / Q000737:chemistry* / Q000378:metabolism*; D017433:Protein Structure, Secondary; D013050:Spectrometry, Fluorescence
chemical_list: D015240:Phorbol 12,13-Dibutyrate; D004533:Egtazic Acid; D011493:Protein Kinase C; D002118:Calcium