Sandbox WWC6: Difference between revisions
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=Hemolysin= | |||
[[Hemolysins]] [https://en.wikipedia.org/wiki/Hemolysin#.CE.B1-hemolysin] are a lipid or protein toxins secreted by pathogens that lyse erythrocyte and some bacterial cell membranes. These toxins belong to a family of microbial exotoxins called cytolysins, which act on a broad number of cells[http://www.uniprot.org/uniprot/P09616]. The primary function of peptide hemolysins is pore formation at the cell membranes creating acytolytic effect, and is achieved by the release of cytosolic ions and small molecules through the hydrophilic, transmembrane portion of the beta-barrel pore[http://www.sciencedirect.com/science/article/pii/S0041010101001532]. | [[Hemolysins]] [https://en.wikipedia.org/wiki/Hemolysin#.CE.B1-hemolysin] are a lipid or protein toxins secreted by pathogens that lyse erythrocyte and some bacterial cell membranes. These toxins belong to a family of microbial exotoxins called cytolysins, which act on a broad number of cells[http://www.uniprot.org/uniprot/P09616]. The primary function of peptide hemolysins is pore formation at the cell membranes creating acytolytic effect, and is achieved by the release of cytosolic ions and small molecules through the hydrophilic, transmembrane portion of the beta-barrel pore[http://www.sciencedirect.com/science/article/pii/S0041010101001532]. | ||
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== Function == | == Function == | ||
Hemolysins are most commonly proteins found in red blood cells that selectively allow for the diffusion of potassium ions across the membrane. <ref >https://en.wikipedia.org/wiki/Hemolysin#cite_note-pmid20692229-3</ref> or lipid biosurfactants that disrupt membrane composition resulting in cell lysis. Hemolysins act through disruption of the cell membrane. <ref>http://www.sciencedirect.com/science/article/pii/S0005273610002610</ref> Pore formation<ref name ="sod"/> is the olgomerization of the pore sunbunits within the membrane. The pore is quickly filled with water, ions, and small molecules that rapidly exit the cell, dissipating ionic gradients and membrane potential. Osmotic pressure causes a rapid swelling of the cell, leading to total rupture of the membrane <ref>http://www.ks.uiuc.edu/Research/hemolysin/<ref>. These proteins are important for some erythrocyte nutrient accession, but cause massive erythrocyte destruction in bacterial infection, specifically responsible forhemolytic anemia, which causes fatigue, pain, arrythmias, and even heart failure in affected individuals.<ref>http://www.nhlbi.nih.gov/health/health-topics/topics/ha/</ref> | |||
==Structure== | ==Structure== | ||
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Alpha hemolysins cause a partial lysis of red blood cells. | Alpha hemolysins cause a partial lysis of red blood cells. | ||
The heptameric pore assembles from water-soluble subunits The transmembrane domain of this water-filled pore is primarily comprised of an anti-parallel beta-barrel | The heptameric pore assembles from water-soluble subunits The transmembrane domain of this water-filled pore is primarily comprised of an anti-parallel beta-barrel | ||
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Beta-hemolysins cause a total lysis of red blood cells. | Beta-hemolysins cause a total lysis of red blood cells. | ||
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== Mechanism of action == | == Mechanism of action== | ||
Four of each of the two subunits assemble in an alternating, circular pattern in the γ-HL pore, whereas seven distinct α-HL protomers assemble in a circular arrangement in the α-HL pore. These typically are comprised of three domains: the cap, rim and stem domains, named for the structural resemblance to a mushroom. The cap domain contains β-sandwiches from each protomer, while just below, the rim domain contains four looping β-strands. The stem domain takes on the antiparallel β-barrel, a portion of which becomes the transmembrane structure. | Four of each of the two subunits assemble in an alternating, circular pattern in the γ-HL pore, whereas seven distinct α-HL protomers assemble in a circular arrangement in the α-HL pore. These typically are comprised of three domains: the cap, rim and stem domains, named for the structural resemblance to a mushroom. The cap domain contains β-sandwiches from each protomer, while just below, the rim domain contains four looping β-strands. The stem domain takes on the antiparallel β-barrel, a portion of which becomes the transmembrane structure. | ||