3SQC

SQUALENE-HOPENE CYCLASE

3SQC の概要

• エントリーDOI: 10.2210/pdb3sqc/pdb
• 分子名称: SQUALENE--HOPENE CYCLASE (2 entities in total)
• 機能のキーワード: triterpene cyclase, monotopic membrane protein, qw-sequence repeat, cholesterol biosynthesis, isomerase
• 由来する生物種: Alicyclobacillus acidocaldarius
• 細胞内の位置: Cell membrane; Peripheral membrane protein: P33247
• タンパク質・核酸の鎖数: 3
• 化学式量合計: 214914.28

構造登録者

Wendt, K.U.,Schulz, G.E. (登録日: 1998-09-04, 公開日: 1999-05-18, 最終更新日: 2024-05-22)

主引用文献

Wendt, K.U.,Lenhart, A.,Schulz, G.E.
The structure of the membrane protein squalene-hopene cyclase at 2.0 A resolution.
J.Mol.Biol., 286:175-187, 1999

PubMed Abstract: Squalene cyclases catalyze a cationic cyclization cascade, which is homologous to a key step in cholesterol biosynthesis. The structure of the enzyme from Alicyclobacillus acidocaldarius has been determined in a new crystal form at 2.0 A resolution (1 A=0.1 nm) and refined to an R-factor of 15.3 % (Rfree=18.7 %). The structure indicates how the initial protonation and the final deprotonation of squalene occur and how the transient carbocations are stabilized. The pathways of the flexible educt squalene from the membrane interior to the active center cavity and of the rigid fused-ring product hopene in the reverse direction are discussed. The enzyme contains eight so-called QW-sequence repeats that fortify the alpha/alpha-barrels by an intricate interaction network. They are unique to the known triterpene cyclases and are presumed to shield these enzymes against the released enthalpy of the highly exergonic catalyzed reaction. The enzyme is a monotopic membrane protein, the membrane-binding interactions of which are described and compared with those of two prostaglandin-H2 synthase isoenzymes, the only other structurally characterized proteins of this type. In the crystals the membrane-binding regions face each other, suggesting a micelle-type detergent structure between them.

PubMed: 9931258
DOI: 10.1006/jmbi.1998.2470

実験手法

X-RAY DIFFRACTION (2.8 Å)