Crystallization and preliminary crystallographic analysis of poly(3-hydroxybutyrate) depolymerase fromBacillus thuringiensis
Poly[(R)-3-hydroxybutyrate] (PHB) is a microbial biopolymer that has been commercialized as biodegradable plastics. The key enzyme for the degradation is PHB depolymerase (PhaZ). A new intracellular PhaZ fromBacillus thuringiensis(BtPhaZ) has been screened for potential applications in polymer biodegradation. Recombinant BtPhaZ was crystallized using 25% polyethylene glycol 3350, 0.2 Mammonium acetate, 0.1 Mbis-tris pH 6.5 at 288 K. The crystals belonged to space groupP1, with unit-cell parametersa= 42.97,b= 83.23,c= 85.50 Å, α = 73.45, β = 82.83, γ = 83.49°. An X-ray diffraction data set was collected to 1.42 Å resolution with anRmergeof 6.4%. Unexpectedly, a molecular-replacement solution was obtained using the crystal structure ofStreptomyces lividanschloroperoxidase as a template, which shares 24% sequence identity to BtPhaZ. This is the first crystal structure of an intracellular poly(3-hydroxybutyrate) depolymerase.