Sandbox Reserved 313: Difference between revisions
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The crystal structure of sphingomyelinase has been solved using the bacterium ''Listeria ivanovii'' and ''Bacillus cereus(Bc-SMase)'' to gain further insight into its catalytic activities <ref name="gp7">PMID: 16595670 </ref>. The overall structure of Bc-SMase has been determined to consist of a β-sandwich with α/β motifs<ref name="gp">PMID: 16595670 </ref>. Through SMase structure identification, it has been determined to be a member of the DNA I-like superfamily having geometrically identical amino acid residues as the enzymes in this superfamily. The only different with SMase, is that it has a unique hydrophobic beta-hairpin structure. The crystal structure revealed that this unique beta-hairpin region has two solvent exposed aromatic amino acids, Trp-284 and Phe-285, on the top which bind to the cell surfaces to catalyze hemolysis. The hydrolysis and hemolytic activity of Bc-SMase occur in a metal ion dependent manner. Bc-Smase is found in complex with divalent metal ions, Co2+, Mg2+ or Ca2+ in the central cleft of this enzyme. The central cleft acts as an active site. | The crystal structure of sphingomyelinase has been solved using the bacterium ''Listeria ivanovii'' and ''Bacillus cereus(Bc-SMase)'' to gain further insight into its catalytic activities <ref name="gp7">PMID: 16595670 </ref>. The overall structure of Bc-SMase has been determined to consist of a β-sandwich with α/β motifs<ref name="gp">PMID: 16595670 </ref>. Through SMase structure identification, it has been determined to be a member of the DNA I-like superfamily having geometrically identical amino acid residues as the enzymes in this superfamily. The only different with SMase, is that it has a unique hydrophobic beta-hairpin structure. The crystal structure revealed that this unique beta-hairpin region has two solvent exposed aromatic amino acids, Trp-284 and Phe-285, on the top which bind to the cell surfaces to catalyze hemolysis. The hydrolysis and hemolytic activity of Bc-SMase occur in a metal ion dependent manner. Bc-Smase is found in complex with divalent metal ions, Co2+, Mg2+ or Ca2+ in the central cleft of this enzyme. The central cleft acts as an active site. | ||
==Active Site== | ==Active Site== | ||
The <scene name='Sandbox_153/Catalyticsite/1'>catalytic site</scene> of the Bc-SMase cotains the amino acid residues Asn-16, Glu-53, Asp-195, Asn-197, and His-296 where Glu-53, Asp-195 and His-296 residues are essential for the hydrolytic activity of the enzyme. In the central cleft, bound Ca2+ displays a hepta-coordination pattern which is different from the Co2+ and Mg2+ bound forms which are in a double-hexa-coordination forming a double octahedral bi-pyramid. Mg2+ binds to Glu-53 and is required for SM hydrolytic activity and Mg2+ with Ca2+ are required for hemolytic activity<ref name="gp">PMID: 16595670 </ref>. | The <scene name='Sandbox_153/Catalyticsite/1'>catalytic site</scene> of the Bc-SMase cotains the amino acid residues Asn-16, Glu-53, Asp-195, Asn-197, and His-296 where Glu-53, Asp-195 and <scene name='Sandbox_Reserved_313/His-296/2'>His-296</scene> residues are essential for the hydrolytic activity of the enzyme. In the central cleft, bound Ca2+ displays a hepta-coordination pattern which is different from the Co2+ and Mg2+ bound forms which are in a double-hexa-coordination forming a double octahedral bi-pyramid. Mg2+ binds to Glu-53 and is required for SM hydrolytic activity and Mg2+ with Ca2+ are required for hemolytic activity<ref name="gp">PMID: 16595670 </ref>. | ||