3vbz
Crystal structure of Taipoxin beta subunit isoform 2Crystal structure of Taipoxin beta subunit isoform 2
Structural highlights
Function[PA22_OXYSC] Snake venom phospholipase A2 (PLA2) that shows high presynaptic neurotoxicity in vertebrata that is independent of catalytic activity (PubMed:2544597, PubMed:10548416 and PubMed:16669624), as well as local myotoxicity when intramuscularly injected into mice (PubMed:16669624). Blocks acetylcholine release in Aplysia neurons (PubMed:8583413), and potentiates proinflammatory cellular signaling (PubMed:12782627). Potentiates glutamate excitoxicity when coinjected into brain of rats (PubMed:10548416). May act by binding in a calcium-dependent fashion and with high affinity to a neuronal-type (N-type) PLA2 receptor, and with very high affinity to a muscle-type (M-type) PLA2 receptor. In vitro, shows a high-specific activity on E.coli membranes and is more efficient on the anionic phospholipid POPG than on the anionic phospholipid POPS or the zwitterionic phospholipid POPC. Exerts catalytically-independent anti-HIV (IC(50) is 35 nM) activity and catalytically-dependent antimalarial activity (IC(50) is 3.1 nM when tested on P.falciparum grown in serum that contains lipoproteins). PLA2 catalyzes the calcium-dependent hydrolysis of the 2-acyl groups in 3-sn-phosphoglycerides.[1] [2] [3] [4] [5] [6] Publication Abstract from PubMedSnake pre-synaptic neurotoxins endowed with phospholipase A(2) activity are potent inducers of paralysis through the specific disruption of the neuromuscular junction pre-synaptic membrane and represent a valuable tool for investigating neuronal degeneration and recovery. They have different structural complexity and a wide range of lethal potency and enzymatic activity, although they share a similar mechanism of action. Although no correlation has been reported between neurotoxicity and enzymatic activity, toxicity increases with structural complexity and phospholipase A(2) oligomers show 10-fold lower LD(50) values compared to their monomeric counterparts. To date, no structural study has been performed on multimeric SPANs with the aim of shedding light on the correlation between structural complexity and neurotoxicity. In the present study, we investigated the structure of taipoxin, a trimeric phospholipase A(2) neurotoxin, as well as that of its subunits, by X-ray crystallography and small angle X-ray scattering analysis. We present the high-resolution structure of two isoforms of the taipoxin beta subunit, which show no neurotoxic activity but enhance the activity of the other subunits in the complex. One isoform shows no structural change that could justify the lack of activity. The other displays three point mutations in critical positions for the catalytic activity. Moreover, we designed a model for the quaternary structure of taipoxin under physiological conditions, in which the three subunits are organized into a flat holotoxin with the substrate binding sockets exposed on the same side of the complex, which suggests a role for this interface in the toxin-membrane interaction. Database The coordinates and structure factors have been deposited in the RCSB Protein Data Bank (http://www.rcsb.org) under accession numbers 3VBZ and 3VCO, corresponding to beta isoforms 1 and 2 respectively Structure digital abstract * taipoxin beta isoform 2 and taipoxin beta isoform 2 bind by x-ray crystallography (View interaction). Structural analysis of trimeric phospholipase A(2) neurotoxin from the Australian taipan snake venom.,Cendron L, Micetic I, Polverino de Laureto P, Paoli M FEBS J. 2012 Jul 6. doi: 10.1111/j.1742-4658.2012.08691.x. PMID:22776098[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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