1sqc: Difference between revisions

The crystal structure of squalene-hopene cyclase from Alicyclobacillus, acidocaldarius was determined at 2.9 angstrom resolution. The mechanism, and sequence of this cyclase are closely related to those of, 2,3-oxidosqualene cyclases that catalyze the cyclization step in, cholesterol biosynthesis. The structure reveals a membrane protein with, membrane-binding characteristics similar to those of prostaglandin-H2, synthase, the only other reported protein of this type. The active site of, the enzyme is located in a large central cavity that is of suitable size, to bind squalene in its required conformation and that is lined by, aromatic residues. The structure supports a mechanism in which the acid, starting the reaction by protonating a carbon-carbon double bond is an, aspartate that is coupled to a histidine. Numerous surface alpha helices, are connected by characteristic QW-motifs (Q is glutamine and W is, tryptophan) that tighten the protein structure, possibly for absorbing the, reaction energy without structural damage.

1SQC is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Alicyclobacillus_acidocaldarius Alicyclobacillus acidocaldarius] with LDA as [http://en.wikipedia.org/wiki/ligand ligand]. Structure known Active Site: LDA. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1SQC OCA].  

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