Cloning, expression, purification, crystallization and preliminary crystallographic analysis of γ-­filamin repeat 23

Human γ-filamin is a protein of 2705 amino-acid residues that localizes mainly in the myofibrillar Z-disc and to smaller extent in the subsarcolemmal region of striated muscle cells. γ-Filamin consists of an N-terminal actin-binding domain followed by a long rod-shaped region. The rod-shaped region consists of 24 immunoglobulin-like domains that form a platform for interaction with different transmembrane, cell-signalling and cytoskeletal proteins. γ-Filamin repeat 23 was indicated as being necessary for binding to the muscle-specific subsarcolemmal proteins γ- and δ-sarcoglycan and the myofibrillar protein FATZ1. The recombinant γ-filamin repeat 23 was crystallized using the hanging-drop vapour-diffusion method, which yielded needle-shaped diffraction-quality crystals. Diffraction data were collected to 2.05 Å resolution using 1.2 Å wavelength synchrotron radiation. Preliminary structural analysis shows one molecule, with predominantly β secondary-structure elements, per asymmetric unit.