Biomaterial Database

Orientation of membrane vesicles from Escherichia coli as detected by freeze-cleave electron microscopy. 1974

K H Altendorf, and L A Staehelin

The application of freeze-cleave electron microscopy to whole cells of Escherichia coli revealed that the particles exposed on the resulting two inner membrane faces are asymmetrically distributed. This method can therefore be used to determine the orientation of membrane vesicles from E. coli. Membrane vesicles freshly prepared in potassium phosphate buffer (K(+)-vesicles) by osmotic lysis of spheroplasts consisted almost entirely of right-side-out vesicles. Their size suggested that each cell gives rise to one vesicle. When the membrane vesicles were subjected to one cycle of freezing and thawing, the number of inside-out vesicles rose to about 25%. However, due to the small size of most of the inside-out vesicles, these contribute only 2 to 3% of the total membrane surface area of the preparation. The inside-out vesicles appear to arise from infoldings of the membrane of right-side-out vesicles. They also accumulate within the latter, thus producing multivesicular membrane sacs. Na(+)-vesicles (vesicles prepared in sodium phosphate buffer) subjected to freezing and thawing appeared to lose structural rigidity more than did K(+)-vesicles. In contrast to the membrane vesicles prepared by the osmotic lysis of spheroplasts, those obtained by breaking intact cells by a single passage through a French pressure cell were uniformly very small (only 40 to 110 nm in diameter); approximately 60 to 80% were inside-out. To reconcile the polarity of the membrane vesicles with the enzymic activities of such preparations, we propose that "dislocation" of membrane proteins occurs during osmotic lysis of spheroplasts.

UI	MeSH Term	Description	Entries
D008722	Methods	A series of steps taken in order to conduct research.	Techniques,Methodological Studies,Methodological Study,Procedures,Studies, Methodological,Study, Methodological,Method,Procedure,Technique
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
D008954	Models, Biological	Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.	Biological Model,Biological Models,Model, Biological,Models, Biologic,Biologic Model,Biologic Models,Model, Biologic
D009995	Osmosis	Tendency of fluids (e.g., water) to move from the less concentrated to the more concentrated side of a semipermeable membrane.	Osmoses
D010710	Phosphates	Inorganic salts of phosphoric acid.	Inorganic Phosphate,Phosphates, Inorganic,Inorganic Phosphates,Orthophosphate,Phosphate,Phosphate, Inorganic
D011188	Potassium	An element in the alkali group of metals with an atomic symbol K, atomic number 19, and atomic weight 39.10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the WATER-ELECTROLYTE BALANCE.
D002021	Buffers	A chemical system that functions to control the levels of specific ions in solution. When the level of hydrogen ion in solution is controlled the system is called a pH buffer.	Buffer
D002458	Cell Fractionation	Techniques to partition various components of the cell into SUBCELLULAR FRACTIONS.	Cell Fractionations,Fractionation, Cell,Fractionations, Cell
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
D004926	Escherichia coli	A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.	Alkalescens-Dispar Group,Bacillus coli,Bacterium coli,Bacterium coli commune,Diffusely Adherent Escherichia coli,E coli,EAggEC,Enteroaggregative Escherichia coli,Enterococcus coli,Diffusely Adherent E. coli,Enteroaggregative E. coli,Enteroinvasive E. coli,Enteroinvasive Escherichia coli