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Single-Molecule Analysis by Biological Nanopores
Published in Shuo Huang, Single-Molecule Tools for Bioanalysis, 2022
Biological nanopores are a category of transmembrane porins with a considerably large pore lumen measuring from 1 to 5 nm in diameter, which are utilized for single-molecule sensing. Reported biological nanopores including S. aureus α-HL [19], MspA [36], Escherichia coli ferric hydroxamate uptake protein A (FhuA) [37], bacteriophage phi29 connector [38], E. coli cytolysin A (ClyA) [39], E. coli outer membrane protein G (OmpG) [40], E. coli outer membrane protein F (OmpF) [41], Actinia fragacea fragaceatoxin C (Frac) [42], E. coli curli production assembly/transport component CsgG (CsgG) [43], and human specificity protein 1 (Sp1) [44] could be similarly utilized as single-molecule sensors (Figure 1.2). The α-HL, which is the most studied biological nanopore, is the most robust nanopore sensor used to date. In nature, it is an exotoxin secreted by the human pathogen S. aureus bacterium. In its heptameric form, α-HL appears as a mushroom-shaped protein (with a cap domain and a stem domain) and a molecular weight of 232.4 kDa. The stem domain, which is embedded in the lipid membrane, is composed of 14 antiparallel β strands that form a cylindrical channel for molecular transportation. The narrowest spot of the cylindrical channel is ~1.4 nm in diameter. It serves as the recognition site for molecular identity discrimination [16] and permits passage only of ssDNA. The cap domain, which has an inner diameter of ~4.5 nm, is capable of accommodating a short fragment of dsDNA.
Toxigenic V. cholerae, V. parahaemolyticus, and V. vulnificus in oysters from the Gulf of Mexico and sold in Mexico City
Published in International Journal of Environmental Health Research, 2019
Carlos L. Fernández-Rendón, Guadalupe Barrera-Escorcia, Irma Wong-Chang, Alfonso Vázquez Botello, Bruno Gómez-Gil, Marcial Leonardo Lizárraga-Partida
Several factors are associated with the virulence of these pathogens. V. cholerae synthesizes a thermostable enterotoxin and several strains produce extracellular enzymes, cytolysins, cytotoxins, hemolysins, capsular polysaccharide, and hemagglutinins (Cabrera-Rodríguez et al. 2008). This species presents around 200 serogroups, of which O1 and O139 produce cholera toxin and causes epidemic cases in the world (Chaudhuri and Chatterjee 2009). Recently the cholix toxin was described (Purdy et al. 2010). In the case of V. parahaemolyticus, the main virulence factors are linked with hemolysin toxins: thermostable direct hemolysin, a pore-forming protein, and related hemolysin that plays a significant role in precipitating the disease (López-Hernández et al. 2015a). Virulence factors in V. vulnificus are associated with capsular polysaccharide, iron acquisition systems, type IV pili, several enzymes (such as proteases, elastase, hyaluronidase, lecithinase, phospholipases, mucinases, and metalloprotease), repeat-in-toxin, and hemolysin/cytolysin (VvhA), among others (Quiñones-Ramírez et al. 2010; Guerrero et al. 2015).
Prevalence of virulence determinants and antibiotic resistance patterns of Enterococcus faecalis strains in patients with community-acquired urinary tract infections in Iran
Published in International Journal of Environmental Health Research, 2018
Abdullah Karimi, Zohreh Ghalavand, Fatemeh Fallah, Parisa Eslami, Mahmoud Parvin, Masoud Alebouyeh, Marjan Rashidan
These factors such as the enterococcal surface protein (Esp), aggregation substance (AS), PavA-like fibronectin-binding protein (EfbA) and adhesion to collagen of E. faecalis (ACE) are involved in colonization of urinary tract tissue, cytolysin (CYL), and gelatinase in escape of the organism from the host immune response and dissemination of the bacterium in the body respectively (Torelli et al. 2012; Gulhan et al. 2015).