抄録
A voltage-regulated phosphatase idenfieid from Ciona intestinalis (Ci-VSP) has ion channel-like voltage sensor with its downstream domain of the cytoplasmic phosphatase (Murata et al, Nature, 2005). A Ci-VSP orthologue from zebrafish (Z-VSP) shows similar properties: phosphoinositide phosphatase activities are voltage-dependent (this meeting, last year),. Interactions among modules are often bidirectional. To address whether the phosphatase domain (PD) modifies properties of voltage sensor domain, we compared gating currents between enzyme-active condition and enzyme-defective condition. When the critical amino acid residue, cysteine, in the active center of PD of Z-VSP, corresponding to the same residue conserved among all protein tyrosine phosphatases (PTP) and PTENs, was mutated to serine, its phosphatase activity was abolished. In this mutant, gating current measured in heterologous expression in HEK tsA201 cells showed unchanged charge versus current (Q-V) curve whereas kinetics was remarkably faster than the wild type protein. In addition, pervanadate, an inhibitor of phosphatase activity of PTP or PTEN, that binds to the phosphatase active site, mimicked the phenotypes of the C-S mutant both of Z-VSP and Ci-VSP. These findings implicate that interactions between VSD and effector domain are bidirectional. [J Physiol Sci. 2007;57 Suppl:S221]
