Structural Basis of the Sphingomyelin Phosphodiesterase Activity in Neutral Sphingomyelinase from Bacillus cereus.Ago, H., Oda, M., Takahashi, M., Tsuge, H., Ochi, S., Katunuma, N., Miyano, M., Sakurai, J.
(2006) J.Biol.Chem. 281: 16157-16167
- PubMed: 16595670
- DOI: 10.1074/jbc.M601089200
- Primary Citation of Related Structures:
- PubMed Abstract:
Sphingomyelinase (SMase) from Bacillus cereus (Bc-SMase) hydrolyzes sphingomyelin to phosphocholine and ceramide in a divalent metal ion-dependent manner. Bc-SMase is a homologue of mammalian neutral SMase (nSMase) and mimics the actions of the endog ...
Sphingomyelinase (SMase) from Bacillus cereus (Bc-SMase) hydrolyzes sphingomyelin to phosphocholine and ceramide in a divalent metal ion-dependent manner. Bc-SMase is a homologue of mammalian neutral SMase (nSMase) and mimics the actions of the endogenous mammalian nSMase in causing differentiation, development, aging, and apoptosis. Thus Bc-SMase may be a good model for the poorly characterized mammalian nSMase. The metal ion activation of sphingomyelinase activity of Bc-SMase was in the order Co2+ > or = Mn2+ > or = Mg2+ > Ca2+ > or = Sr2+. The first crystal structures of Bc-SMase bound to Co2+, Mg2+, or Ca2+ were determined. The water-bridged double divalent metal ions at the center of the cleft in both the Co2+- and Mg2+-bound forms were concluded to be the catalytic architecture required for sphingomyelinase activity. In contrast, the architecture of Ca2+ binding at the site showed only one binding site. A further single metal-binding site exists at one side edge of the cleft. Based on the highly conserved nature of the residues of the binding sites, the crystal structure of Bc-SMase with bound Mg2+ or Co2+ may provide a common structural framework applicable to phosphohydrolases belonging to the DNase I-like folding superfamily. In addition, the structural features and site-directed mutagenesis suggest that the specific beta-hairpin with the aromatic amino acid residues participates in binding to the membrane-bound sphingomyelin substrate.
Structural Biophysics Laboratory, RIKEN SPring-8 Center, Harima Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan. email@example.com