Publication Date:
1997-09-20
Description:
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.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wendt, K U -- Poralla, K -- Schulz, G E -- New York, N.Y. -- Science. 1997 Sep 19;277(5333):1811-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institut fur Organische Chemie und Biochemie, Albertstrasse 21, D-79104 Freiburg im Breisgau, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9295270" target="_blank"〉PubMed〈/a〉
Keywords:
Amino Acid Sequence
;
Bacillaceae/*enzymology
;
Binding Sites
;
Cell Membrane/enzymology
;
Crystallization
;
Crystallography, X-Ray
;
Cyclization
;
Dimerization
;
Humans
;
Hydrogen Bonding
;
*Intramolecular Transferases
;
Isomerases/*chemistry/metabolism
;
Models, Molecular
;
Molecular Sequence Data
;
*Protein Conformation
;
Protein Folding
;
Protein Structure, Secondary
;
Recombinant Proteins/chemistry/metabolism
;
Sequence Alignment
;
Squalene/metabolism
;
Thermodynamics
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
,
Chemistry and Pharmacology
,
Computer Science
,
Medicine
,
Natural Sciences in General
,
Physics
