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Beta barrels also function within endosymbiont derived organelles such as mitochondria and chloroplasts to transport proteins. [8] Within the mitochondrion two complexes exist with beta barrels serving as the pore forming subunit, Tom40 of the Translocase of the outer membrane, and Sam50 of the Sorting and assembly machinery. The chloroplast ...
In humans, 27% of all proteins have been estimated to be alpha-helical membrane proteins. [6] Beta-barrel proteins are so far found only in outer membranes of gram-negative bacteria, cell walls of gram-positive bacteria, outer membranes of mitochondria and chloroplasts, or can be secreted as pore-forming toxins. All beta-barrel transmembrane ...
Porins are beta barrel proteins that cross a cellular membrane and act as a pore, through which molecules can diffuse. [1] Unlike other membrane transport proteins, porins are large enough to allow passive diffusion, i.e., they act as channels that are specific to different types of molecules.
Schematic diagram of the 2D structure of aquaporin 1 depicting the six transmembrane alpha-helices and the five interhelical loop regions A-E The 3D structure of aquaporin Z highlighting the 'hourglass'-shaped water channel that cuts through the center of the protein. Aquaporin proteins are composed of a bundle of six transmembrane α-helices ...
OmpA-like transmembrane domain is an evolutionarily conserved domain of bacterial outer membrane proteins. This domain consists of an eight-stranded beta barrel. [1] OmpA is the predominant cell surface antigen in enterobacteria found in about 100,000 copies per cell. [2] The expression of OmpA is tightly regulated by a variety of mechanisms.
A transmembrane domain (TMD, TM domain) is a membrane-spanning protein domain.TMDs may consist of one or several alpha-helices or a transmembrane beta barrel.Because the interior of the lipid bilayer is hydrophobic, the amino acid residues in TMDs are often hydrophobic, although proteins such as membrane pumps and ion channels can contain polar residues.
Although maltoporin contains a wider beta-barrel than the porins of the GBP and RPP families, it exhibits a narrower channel, showing only 5% of the ionic conductance of the latter porins. The Rhodobacter PorCa Protein, the only well characterized member of the RPP family, was the first porin to yield its three-dimensional structure by X-ray ...
OMPdb is a dedicated database that contains beta barrel (β-barrel) outer membrane proteins from Gram-negative bacteria. [1] Such proteins are responsible for a broad range of important functions, like passive nutrient uptake, active transport of large molecules, protein secretion, as well as adhesion to host cells, through which bacteria expose their virulence activity.