title: How a G protein binds a membrane.
abstract: Heterotrimeric G proteins interact with receptors and effectors at the membrane-cytoplasm interface. Structures of soluble forms have not revealed how they interact with membranes. We have used electron crystallography to determine the structure in ice of a helical array of the photoreceptor G protein, transducin, bound to the surface of a tubular lipid bilayer. The protein binds to the membrane with a very small area of contact, restricted to two points, between the surface of the protein and the surface of the lipids. Fitting the x-ray structure into the membrane-bound structure reveals one membrane contact near the lipidated Ggamma C terminus and Galpha N terminus, and another near the Galpha C terminus. The narrowness of the tethers to the lipid bilayer provides flexibility for the protein to adopt multiple orientations on the membrane, and leaves most of the G protein surface area available for protein-protein interactions.
authors.affiliation: Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
authors.forename: Zhixian
authors.initials: Z
authors.lastname: Zhang
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Melia
authors.forename: Feng
authors.initials: F
authors.lastname: He
authors.forename: Ching
authors.initials: C
authors.lastname: Yuan
authors.forename: Amy
authors.initials: A
authors.lastname: McGough
authors.forename: Michael F
authors.initials: MF
authors.lastname: Schmid
authors.forename: Theodore G
authors.initials: TG
authors.lastname: Wensel
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism*; D003460:Crystallization; D018360:Crystallography, X-Ray; D007053:Ice; D007091:Image Processing, Computer-Assisted; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D008563:Membrane Lipids / Q000737:chemistry / Q000378:metabolism; D008854:Microscopy, Electron; D008958:Models, Molecular; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D012374:Rod Cell Outer Segment / Q000737:chemistry; D015293:Transducin / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D007053:Ice; D008051:Lipid Bilayers; D008563:Membrane Lipids; D010446:Peptide Fragments; D015293:Transducin