Basic phospholipase A2 homolog bothropstoxin-I

UniProtKB accession:  Q90249

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UniProtKB description:  Snake venom phospholipase A2 homolog that lacks enzymatic activity. Shows local myotoxic activity (PubMed:11018293, PubMed:12079495, PubMed:31906173). Induces inflammation, since it induces edema and leukocytes infiltration (PubMed:11018293, PubMed:31906173). In addition, it induces NLRP3 NLRP3, ASC (PYCARD), caspase-1 (CASP1), and IL-1beta (IL1B) gene expression in the gastrocnemius muscle, showing that it is able to activate NLRP3 inflammasome (PubMed:31906173). It also damages artificial and myoblast membranes by a calcium-independent mechanism, has bactericidal activity, and induces neuromuscular blockade (PubMed:27531710). A model of myotoxic mechanism has been proposed: an apo Lys49-PLA2 is activated by the entrance of a hydrophobic molecule (e.g. fatty acid) at the hydrophobic channel of the protein leading to a reorientation of a monomer (PubMed:27531710) (By similarity). This reorientation causes a transition between 'inactive' to 'active' states, causing alignment of C-terminal and membrane-docking sites (MDoS) side-by-side and putting the membrane-disruption sites (MDiS) in the same plane, exposed to solvent and in a symmetric position for both monomers (PubMed:27531710) (By similarity). The MDoS region stabilizes the toxin on membrane by the interaction of charged residues with phospholipid head groups (PubMed:27531710) (By similarity). Subsequently, the MDiS region destabilizes the membrane with penetration of hydrophobic residues (PubMed:27531710) (By similarity). This insertion causes a disorganization of the membrane, allowing an uncontrolled influx of ions (i.e. calcium and sodium), and eventually triggering irreversible intracellular alterations and cell death (PubMed:27531710) (By similarity).