Dynamic structural rearrangements and functional regulation of voltage‐sensing phosphatase

• Published in: The Journal of physiology 2019-01, Vol.597 (1), p.29-40
• Main Authors: Sakata, Souhei, Okamura, Yasushi
• Format: Article
• Language: English
• Subjects: amber suppressor tRNA; Amino acids; Amino Acids - chemistry; Amino Acids - genetics; Animals; Cell Membrane - physiology; Cell membranes; Depolarization; Enzymatic activity; Enzymes; Fluorescence; Fluorescence resonance energy transfer; Ion channels; Membrane potential; Phosphatase; phosphoinositide; Phosphoric Monoester Hydrolases - chemistry; Phosphoric Monoester Hydrolases - physiology; Protein Domains; PTEN protein; Structure-function relationships; Topical Review; Topical Reviews; Tumors; Voltage; voltage sensor
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/JP274113

The voltage‐sensing phosphatase (VSP) consists of a voltage sensor domain (VSD) and a cytoplasmic catalytic region. The latter contains a phosphatase domain and a C2 domain, showing remarkable similarity to the tumour suppressor enzyme PTEN. In VSP, membrane depolarization induces a conformational change in the VSD, which activates the phosphoinositide phosphatase. The final outcome in VSP is enzymatic activity in the cytoplasmic region, unlike in voltage‐gated ion channels where conformational change of the transmembrane pore is induced by the VSD. Therefore, it is crucial to detect structural change in the cytoplasmic catalytic region to gain insights into the operating mechanisms of VSP. This review summarizes a recent study in which a method of genetic incorporation of a non‐canonical amino acid, Anap, was used to detect dynamic membrane voltage‐controlled rearrangements of the structure of the catalytic region of sea squirt VSP (Ci‐VSP). Upon membrane depolarization, both the phosphatase domain and the C2 domain move in a similar time frame, suggesting that the two regions are coupled to each other. Measurement of Förster resonance energy transfer (FRET) between Anap introduced into the C2 domain of Ci‐VSP and dipicrylamine in the cell membrane suggested no large movement of the enzyme towards the membrane. Fluorescence changes in Anap induced by different membrane potentials indicate the presence of multiple conformations of the active enzyme. A fluorescent unnatural amino acid, Anap, was genetically incorporated into the catalytic domain of Ci‐VSP in Xenopus oocytes. Measuring the fluorescence uncovered the conformation changes associated with catalytic activity of Ci‐VSP.