title: Allosteric substrate switching in a voltage-sensing lipid phosphatase.
abstract: Allostery provides a critical control over enzyme activity, biasing the catalytic site between inactive and active states. We found that the Ciona intestinalis voltage-sensing phosphatase (Ci-VSP), which modifies phosphoinositide signaling lipids (PIPs), has not one but two sequential active states with distinct substrate specificities, whose occupancy is allosterically controlled by sequential conformations of the voltage-sensing domain (VSD). Using fast fluorescence resonance energy transfer (FRET) reporters of PIPs to monitor enzyme activity and voltage-clamp fluorometry to monitor conformational changes in the VSD, we found that Ci-VSP switches from inactive to a PIP3-preferring active state when the VSD undergoes an initial voltage-sensing motion and then into a second PIP2-preferring active state when the VSD activates fully. This two-step allosteric control over a dual-specificity enzyme enables voltage to shape PIP concentrations in time, and provides a mechanism for the complex modulation of PIP-regulated ion channels, transporters, cell motility, endocytosis and exocytosis.
authors.affiliation: Biophysics Graduate Group, University of California, Berkeley, California, USA.
authors.forename: Sasha S
authors.initials: SS
authors.lastname: Grimm
authors.affiliation: Biophysics Graduate Group, University of California, Berkeley, California, USA.|Department of Molecular and Cell Biology, University of California, Berkeley, California, USA.|Helen Wills Neuroscience Institute, University of California, Berkeley, California, USA.|Physical Bioscience Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA.
authors.forename: Ehud Y
authors.initials: EY
authors.lastname: Isacoff
mesh_terms: D000494:Allosteric Regulation; D000495:Allosteric Site; D000818:Animals; D020134:Catalytic Domain; D002938:Ciona intestinalis / Q000201:enzymology; D031541:Fluorescence Resonance Energy Transfer; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009865:Oocytes; D018408:Patch-Clamp Techniques; D010716:Phosphatidylinositols / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity; D014982:Xenopus laevis
chemical_list: D010716:Phosphatidylinositols; C509671:voltage-sensor-containing phosphatase, Ciona intestinalis; D010744:Phosphoric Monoester Hydrolases