Crystallization and preliminary crystallographic analysis of selenomethionine-labelled progesterone 5β-reductase from Digitalis lanata Ehrh

Progesterone 5 beta-reductase (5 beta-POR) catalyzes the reduction of progesterone to 5 beta-pregnane-3,20-dione and is the first stereospecific enzyme in the putative biosynthetic pathway of Digitalis cardenolides. Selenomethionine- derivatized 5 beta-POR from D. lanata was successfully overproduced and crystallized. The crystals belong to space group P4(3)2(1)2, with unit-cell parameters a = 71.73, c = 186.64 angstrom. A MAD data set collected at 2.7 angstrom resolution allowed the identification of six out of eight possible Se-atom positions. A first inspection of the MAD-phased electron-density map shows that 5 beta-POR is a Rossmann-type reductase and the quality of the map is such that it is anticipated that a complete atomic model of 5 beta-POR will readily be built.