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Alpha-toxin has been shown to play a role in pathogenesis of disease, as hly knockout strains show reductions in invasiveness and virulence. [2] The dosage of toxin can result in two different modes of activity. Low concentrations of toxin bind to specific, but unidentified, cell surface receptors and form the heptameric pores.
Figure 1 shows the pore-form of α-hemolysin, the first crystal structure of a β-PFT in its pore-form. 7 α-hemolysin monomers come together to create the mushroom-shaped pore. The 'cap' of the mushroom sits on the surface of the cell, and the 'stalk' of the mushroom penetrates the cell membrane, rendering it permeable (see later).
Alpha-hemolysin from uropathogenic E. coli produces extra-intestinal infections and can cause cystitis, pyelonephritis, and sepsis. Alpha-hemolysin from Staphylococcus aureus can cause severe diseases, such as pneumonia. Aerolysin from Aeromonas sobria infects the intestinal tract, but it might also cause sepsis and meningitis.
When alpha-hemolysis (α-hemolysis) is present, the agar under the colony is light and greenish. Streptococcus pneumoniae and a group of oral streptococci (Streptococcus viridans or viridans streptococci) display alpha-hemolysis. This is sometimes called green hemolysis because of the color change in the agar.
C. perfringens alpha toxin (lecithinase) causes myonecrosis and hemolysis. The lecithinase of S. aureus is used in detection of coagulase-positive strains, because of high link between lecithinase activity and coagulase activity.
The toxin is a 1706 residue-long polypeptide that consists of an N-terminal ~400 residue-long adenylate cyclase (AC) enzyme that is linked to a characteristic RTX hemolysin (Hly) moiety of ~1300 residues. This Hly moiety itself consists of four functional subdomains, comprising: (i) a hydrophobic pore-forming domain ; (ii) an activation domain ...
“I’m a f*king alpha.” Those records also show employees discussing Coristine’s conduct and him allegedly leaking information to a competitor. “Edward has been terminated for leaking ...
Alpha hemolysin (αHL), a nanopore from bacteria that causes lysis of red blood cells, has been studied for over 15 years. [20] To this point, studies have shown that all four bases can be identified using ionic current measured across the αHL pore. [21] [22] The structure of αHL is advantageous to identify specific bases moving through the ...