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.
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
Ke-He
KH
Ruan
Shui-Ping
SP
So
Weida
W
Zheng
Jiaxin
J
Wu
Dawei
D
Li
Jennifer
J
Kung
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