Biomaterial Database

A three-dimensional molecular assembly model of a lipoprotein from the Escherichia coli outer membrane. 1974

M Inouye

From the complete amino-acid sequence of a lipoprotein from the outer membrane of E. coli, a three-dimensional molecular assembly model was constructed. It is proposed that the model provides a tubular hydrophilic channel through the outer membrane, which serves as a passive diffusion pore. An alpha-helix is constructed from the sequence, and six of them are arranged to form a superhelix with a hydrophilic interior and hydrophobic outer surface. The superhelical assembly is stabilized by seven ionic interactions between adjacent alpha-helices. Since the height of the assembly is 76 A, it could be inserted into the outer membrane and span the full 75-A thick membrane. The assembly is stabilized in the outer membrane not only by hydrophobic interaction between the surface of the assembly and the lipid bilayer, but also by three hydrocarbon chains of fatty acids linked to the amino-terminal end of the lipoprotein, which are flipped back along the assembly and inserted into the lipid bilayer of the outer membrane. Any two alpha-helices in an assembly are linked to the peptidoglycan at their carboxyl-terminal ends so that the outer membrane is anchored on the peptidoglycan layer. Six or more alpha-helices can form an assembly of this type. However, assuming that an assembly consists of six helices, there are 1.25 x 10(5) per cell hydrophilic channels of a diameter of 12.5 A and 35% of the cell surface is occupied by the assemblies.

UI	MeSH Term	Description	Entries
D008074	Lipoproteins	Lipid-protein complexes involved in the transportation and metabolism of lipids in the body. They are spherical particles consisting of a hydrophobic core of TRIGLYCERIDES and CHOLESTEROL ESTERS surrounded by a layer of hydrophilic free CHOLESTEROL; PHOSPHOLIPIDS; and APOLIPOPROTEINS. Lipoproteins are classified by their varying buoyant density and sizes.	Circulating Lipoproteins,Lipoprotein,Lipoproteins, Circulating
D008961	Models, Structural	A representation, generally small in scale, to show the structure, construction, or appearance of something. (From Random House Unabridged Dictionary, 2d ed)	Model, Structural,Structural Model,Structural Models
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
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
D000595	Amino Acid Sequence	The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.	Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D001426	Bacterial Proteins	Proteins found in any species of bacterium.	Bacterial Gene Products,Bacterial Gene Proteins,Gene Products, Bacterial,Bacterial Gene Product,Bacterial Gene Protein,Bacterial Protein,Gene Product, Bacterial,Gene Protein, Bacterial,Gene Proteins, Bacterial,Protein, Bacterial,Proteins, Bacterial