1SQC

SQUALENE-HOPENE-CYCLASE FROM ALICYCLOBACILLUS ACIDOCALDARIUS

Summary for 1SQC

• Entry DOI: 10.2210/pdb1sqc/pdb
• Descriptor: SQUALENE-HOPENE CYCLASE, LAURYL DIMETHYLAMINE-N-OXIDE (3 entities in total)
• Functional Keywords: isomerase, membrane protein, terpenoid metabolism, squalene to hopene (hop-22, 29-ene) and diplopterol (hopane-22-ol)
• Biological source: Alicyclobacillus acidocaldarius
• Cellular location: Cell membrane; Peripheral membrane protein: P33247
• Total number of polymer chains: 1
• Total formula weight: 71879.44

Authors

Wendt, K.U.,Schulz, G.E. (deposition date: 1997-09-01, release date: 1997-12-17, Last modification date: 2024-02-14)

Primary citation

Wendt, K.U.,Poralla, K.,Schulz, G.E.
Structure and function of a squalene cyclase.
Science, 277:1811-1815, 1997

PubMed Abstract: 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.

PubMed: 9295270
DOI: 10.1126/science.277.5333.1811

Experimental method

X-RAY DIFFRACTION (2.85 Å)