Crystallization and preliminary X-ray crystallographic studies of mavicyanin from Cucurbita pepo medullosa

Mavicyanin isolated from Cucurbita pepo medullosa is a glycosylated protein containing a single polypeptide chain of 109 amino-acid residues and is a member of the phytocyanin subclass of cupredoxins. Non-glycosylated recombinant mavicyanin, which was expressed in Escherichia coli, was crystallized by the hanging-drop vapour-diffusion method with ammonium sulfate as the precipitant at pH 5.5. The crystals belonged to the hexagonal space group P6(1) (or P6(5)), with unit-cell parameters a = 64.0, c = 245.0 A, four molecules per asymmetric unit and a solvent content of 59%. X-ray diffraction data were collected to 1.6 A resolution. To solve the structure of mavicyanin, the MAD method as well as a Patterson search method using the structure of stellacyanin as a starting model are presently being utilized.