Multiple crystal forms of NN′-diacetylchitobiose deacetylase from Pyrococcus furiosus

摘要

Native N,N′-diacetylchitobiose deacetylase from Pyrococcus furiosus (Pf-Dac) and its selenomethionine derivative (Se-Pf-Dac) were crystallized and analyzed in the presence and absence of cadmium ion. The four crystal structures fell into three different crystal-packing groups, with the cadmium-free Pf-Dac and Se-Pf-Dac belonging to the same space group, with homologous unit-cell parameters. The crystal structures in the presence of cadmium contained distorted octahedral cadmium complexes coordinated by three chlorides, two O atoms and an S or Se atom from the N-terminal methionine or selenomethionine, respectively. The N-terminal cadmium complex was involved in crystal contacts between symmetry-related molecules through hydrogen bonding to the N-termini. While all six N-termini of Se-Pf-Dac were involved in cadmium-complex formation, only two of the Pf-Dac N-termini participated in complex formation in the Cd-containing crystal, resulting in different crystal forms. These differences are discussed in light of the higher stability of the Cd—Se bond than the Cd—S bond. This work provides an example of the contribution of cadmium towards determining protein crystal quality and packing depending on the use of the native protein or the selenomethionine derivative.