CRYSTALLIZATION OF THE NADP-DEPENDENT BETA-KETO ACYL CARRIER PROTEIN REDUCTASE FROM ESCHERICHIA-COLI

The NADP-dependent beta-keto acyl carrier protein reductase (BKR) from E. coli has been crystallized by the hanging-drop method of vapour di ffusion using poly(ethylene glycol) of average molecular weight 1450. The crystals belong to the hexagonal space group P6(1)22 or P6(5)22 wi th unit-cell dimensions a = b = 67.8, c = 355.8 Angstrom. Calculated v alues for V-m and consideration of the packing suggest that the asymme tric unit contains a dimer. BKR catalyses the first reductive step in the elongation cycle of fatty-acid biosynthesis. It shares extensive s equence homology with the enzyme which catalyzes the second reductive step in the cycle, enoyl acyl carrier protein reductase (ENR), and thu s provides an opportunity to study the evolution of enzyme function in a metabolic pathway. The structure determination will permit the anal ysis of the molecular basis of its catalytic mechanism and substrate s pecificity.