Solution structure and topology of the N-terminal membrane anchor domain of a microsomal cytochrome P450: prostaglandin I2 synthase.
The three-dimensional structure of a synthetic peptide corresponding to the N-terminal membrane anchor domain (residues 1-25) of prostaglandin I(2) synthase (also known as cytochrome P450 8A1), an eicosanoid-synthesizing microsomal cytochrome P450, has been determined by two-dimensional (1)H NMR spectroscopy in trifluoroethanol and dodecylphosphocholine which mimic the hydrophobic membrane environment. A combination of two-dimensional NMR experiments, including NOESY, TOCSY and double-quantum-filtered COSY, was used to obtain complete (1)H NMR assignments for the peptide. Using the NOE data obtained from the assignments and simulated annealing calculations, the N-terminal membrane domain reveals a bent-shaped structure comprised of an initial helix (residues 3-11), followed by a turn (residues 12-16) and a further atypical helix (residues 17-23). The hydrophobic side chains of the helix and turn segments (residues 1-20) are proposed to interact with the hydrocarbon interior of the phospholipid bilayer of the endoplasmic reticulum (ER) membrane. The hydrophilic side chains of residues 21-25 (Arg-Arg-Arg-Thr-Arg) point away from the hydrophobic residues 1-20 and are expected to be exposed to the aqueous environment on the cytoplasmic side of the ER membrane. The distance between residues 1 and 20 is approx. 20 A (1 A=0.1 nm), less than the thickness of a lipid bilayer. This indicates that the N-terminal membrane anchor domain of prostaglandin I(2) synthase does not penetrate the ER membrane.
Ruan
Ke-He
KH
The Vascular Biology Research Center and Division of Hematology, Department of Internal Medicine, The University of Texas Health Science Center, Houston, TX 77030, USA. kruan@uth.tmc.edu
So
Shui-Ping
SP
Zheng
Weida
W
Wu
Jiaxin
J
Li
Dawei
D
Kung
Jennifer
J
D000595:Amino Acid Sequence; D002942:Circular Dichroism; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry*; D006801:Humans; D019746:Intramolecular Oxidoreductases / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008861:Microsomes / Q000201:enzymology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism; D010455:Peptides / Q000737:chemistry; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary
D010455:Peptides; D003577:Cytochrome P-450 Enzyme System; D019746:Intramolecular Oxidoreductases; C022461:prostacyclin synthetase; D010100:Oxygen