Preparation and crystallization of selenomethionyl dextranase from Penicillium minioluteum expressed in Pichia pastoris

Dextranase from the fungus Penicillium minioluteum hydrolyses α-­1,6-glycosidic bonds in dextran polymers. The enzyme has been expressed in Pichia pastoris in the presence of selenomethionine (SeMet). The level of SeMet incorporation was estimated by amino-acid analysis to be 50%. The protein has been crystallized in space group P2₁2₁2, with unit-cell parameters a = 103.6, b = 115.3, c = 49.8 Å and one molecule per asymmetric unit. The crystals diffract to 2.0 Å and the presence of SeMet in the crystals has been confirmed by an X-ray absorption spectrum.