Overexpression, crystallization and preliminary X-ray crystallographic analysis of the C-terminal cytosolic domain of mouse anoctamin 1.

Transmembrane protein 16A (TMEM16A, also known as anoctamin 1; ANO1) is a bona fide Ca(2+)-activated chloride channel that is activated by intracellular Ca(2+)- and Ca(2+)-mobilizing stimuli and plays important roles in a variety of physiological functions. To elucidate the structural features of ANO1, structural analysis of the C-terminal cytosolic domain of mouse ANO1 (mANO1-CTD) was initiated. mANO1-CTD was overexpressed in Escherichia coli and was crystallized at 297 K using a reservoir solution consisting of 0.2 M sodium acetate trihydrate, 0.1 M Tris-HCl pH 8.5 and 30%(w/v) PEG 4000. X-ray diffraction data were collected to 2.3 Å resolution. The crystals belonged to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 73.96, b = 103.73, c = 114.71 Å. If it is assumed that eight copies of a monomer molecule are present in the crystallographic asymmetric unit, the crystal volume per protein mass (V(M)) is 2.38 Å(3) Da(-1) and the solvent content is 48.38%. Attempts to solve the structure of mANO1-CTD by the MAD method using selenomethionine-labelled mANO1-CTD or heavy-atom-derivatized crystals are in progress.