Mapping the lipid-exposed surfaces of membrane proteins.
Phospholamban forms a stable complex of five long transmembrane helices. We show that the relative rotational orientation of the helices in the pentameric complex can be distinguished by S-H to S-D exchange of cysteine sulphydryl groups located in the transmembrane segment of the protein and exposed to the lipid environment. Of the three cysteine residues in phospholamban, two residues (Cys 36 and Cys 46) are oriented towards the helix interface and protected from exchange, while the third cysteine (Cys 41) is oriented towards the lipid interface and undergoes exchange with water diffused into the bilayer. Distinguishing the external and internal faces of a membrane protein by sulphydryl exchange provides a general approach for determining the three-dimensional fold of membrane proteins and enhances model building efforts to generate high-resolution structures.
Arkin
I T
IT
Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
MacKenzie
K R
KR
Fisher
L
L
Aimoto
S
S
Engelman
D M
DM
Smith
S O
SO
D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D003545:Cysteine; D008051:Lipid Bilayers; D046911:Macromolecular Substances; D008563:Membrane Lipids / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D017510:Protein Folding; D017433:Protein Structure, Secondary; D013499:Surface Properties; D000099211:Phospholamban
D000251:Adenosine Triphosphatases; D002135:Calcium-Binding Proteins; D003545:Cysteine; D008051:Lipid Bilayers; D046911:Macromolecular Substances; D008563:Membrane Lipids; D008565:Membrane Proteins; D000099211:Phospholamban