Structural analysis of cloned plasma membrane proteins by freeze-fracture electron microscopy. 1998

S Eskandari, and E M Wright, and M Kreman, and D M Starace, and G A Zampighi
Department of Physiology, University of California at Los Angeles School of Medicine, Los Angeles, CA 90095-1751, USA. sepehr@physiology.medsch.ucla.edu

We have used freeze-fracture electron microscopy to examine the oligomeric structure and molecular asymmetry of integral plasma membrane proteins. Recombinant plasma membrane proteins were functionally expressed in Xenopus laevis oocytes, and the dimensions of their freeze-fracture particles were analyzed. To characterize the freeze-fracture particles, we compared the particle cross-sectional area of proteins with alpha-helical transmembrane domains (opsin, aquaporin 1, and a connexin) with their area obtained from existing maps calculated from two-dimensional crystals. We show that the cross-sectional area of the freeze-fracture particles corresponds to the area of the transmembrane domain of the protein, and that the protein cross-sectional area varies linearly with the number membrane-spanning helices. On average, each helix occupies 1.40 +/- 0.03 nm2. By using this information, we examined members from three classes of plasma membrane proteins: two ion channels, the cystic fibrosis transmembrane conductance regulator and connexin 50 hemi-channel; a water channel, the major intrinsic protein (the aquaporin 0); and a cotransporter, the Na+/glucose cotransporter. Our results suggest that the cystic fibrosis transmembrane conductance regulator is a dimer containing 25 +/- 2 transmembrane helices, connexin 50 is a hexamer containing 24 +/- 3 helices, the major intrinsic protein is a tetramer containing 24 +/- 3 helices, and the Na+/glucose cotransporter is an asymmetrical monomer containing 15 +/- 2 helices.

UI MeSH Term Description Entries
D007473 Ion Channels Gated, ion-selective glycoproteins that traverse membranes. The stimulus for ION CHANNEL GATING can be due to a variety of stimuli such as LIGANDS, a TRANSMEMBRANE POTENTIAL DIFFERENCE, mechanical deformation or through INTRACELLULAR SIGNALING PEPTIDES AND PROTEINS. Membrane Channels,Ion Channel,Ionic Channel,Ionic Channels,Membrane Channel,Channel, Ion,Channel, Ionic,Channel, Membrane,Channels, Ion,Channels, Ionic,Channels, Membrane
D008562 Membrane Glycoproteins Glycoproteins found on the membrane or surface of cells. Cell Surface Glycoproteins,Surface Glycoproteins,Cell Surface Glycoprotein,Membrane Glycoprotein,Surface Glycoprotein,Glycoprotein, Cell Surface,Glycoprotein, Membrane,Glycoprotein, Surface,Glycoproteins, Cell Surface,Glycoproteins, Membrane,Glycoproteins, Surface,Surface Glycoprotein, Cell,Surface Glycoproteins, Cell
D008565 Membrane Proteins Proteins which are found in membranes including cellular and intracellular membranes. They consist of two types, peripheral and integral proteins. They include most membrane-associated enzymes, antigenic proteins, transport proteins, and drug, hormone, and lectin receptors. Cell Membrane Protein,Cell Membrane Proteins,Cell Surface Protein,Cell Surface Proteins,Integral Membrane Proteins,Membrane-Associated Protein,Surface Protein,Surface Proteins,Integral Membrane Protein,Membrane Protein,Membrane-Associated Proteins,Membrane Associated Protein,Membrane Associated Proteins,Membrane Protein, Cell,Membrane Protein, Integral,Membrane Proteins, Integral,Protein, Cell Membrane,Protein, Cell Surface,Protein, Integral Membrane,Protein, Membrane,Protein, Membrane-Associated,Protein, Surface,Proteins, Cell Membrane,Proteins, Cell Surface,Proteins, Integral Membrane,Proteins, Membrane,Proteins, Membrane-Associated,Proteins, Surface,Surface Protein, Cell
D008854 Microscopy, Electron Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen. Electron Microscopy
D009004 Monosaccharide Transport Proteins A large group of membrane transport proteins that shuttle MONOSACCHARIDES across CELL MEMBRANES. Hexose Transport Proteins,Band 4.5 Preactin,Erythrocyte Band 4.5 Protein,Glucose Transport-Inducing Protein,Hexose Transporter,4.5 Preactin, Band,Glucose Transport Inducing Protein,Preactin, Band 4.5,Proteins, Monosaccharide Transport,Transport Proteins, Hexose,Transport Proteins, Monosaccharide,Transport-Inducing Protein, Glucose
D009865 Oocytes Female germ cells derived from OOGONIA and termed OOCYTES when they enter MEIOSIS. The primary oocytes begin meiosis but are arrested at the diplotene state until OVULATION at PUBERTY to give rise to haploid secondary oocytes or ova (OVUM). Ovocytes,Oocyte,Ovocyte
D010316 Particle Size Relating to the size of solids. Particle Sizes,Size, Particle,Sizes, Particle
D011487 Protein Conformation The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain). Conformation, Protein,Conformations, Protein,Protein Conformations
D011994 Recombinant Proteins Proteins prepared by recombinant DNA technology. Biosynthetic Protein,Biosynthetic Proteins,DNA Recombinant Proteins,Recombinant Protein,Proteins, Biosynthetic,Proteins, Recombinant DNA,DNA Proteins, Recombinant,Protein, Biosynthetic,Protein, Recombinant,Proteins, DNA Recombinant,Proteins, Recombinant,Recombinant DNA Proteins,Recombinant Proteins, DNA
D002462 Cell Membrane The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells. Plasma Membrane,Cytoplasmic Membrane,Cell Membranes,Cytoplasmic Membranes,Membrane, Cell,Membrane, Cytoplasmic,Membrane, Plasma,Membranes, Cell,Membranes, Cytoplasmic,Membranes, Plasma,Plasma Membranes

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