Botulinum neurotoxin A changes conformation upon binding to ganglioside GT1b.
ABSTRACT In this work, the kinetics of the binding of botulinum neurotoxin A (BoNT/A) to ganglioside GT1b were studied using surface plasmon resonance (SPR). The neurotoxin bound polysialylated gangliosides, and that binding was affected by the ionic strength of the buffer. Although the level of binding was decreased at higher ionic strengths, it could be easily observed in Tris buffer, containing 150 mM NaCl. Data analysis revealed that the binding of BoNT/A to a GT1b-containing phospholipid monolayer did not fit a traditional 1:1 model. Subsequent studies, in which the time of contact between BoNT/A and GT1b was varied, indicated that the BoNT/A-GT1b complex became more stable over time, as evidenced by its reduced rate of dissociation. Circular dichroism indicated that when BoNT/A was incubated with GT1b, it underwent a conformational change that resulted in an increase in alpha-helix content and a decrease in beta-sheet content. Therefore, the SPR kinetic data were fit to a conformational change model and kinetic rate constants determined. The apparent K(D) values obtained for the binding of BoNT/A to ganglioside GT1b ranged from 2.83 x 10(-7) to 1.86 x 10(-7) M, depending on the ionic strength of the buffer.
Article: Crystal structure of botulinum neurotoxin type A in complex with the cell surface co-receptor GT1b-insight into the toxin-neuron interaction.[show abstract] [hide abstract]
ABSTRACT: Botulinum neurotoxins have a very high affinity and specificity for their target cells requiring two different co-receptors located on the neuronal cell surface. Different toxin serotypes have different protein receptors; yet, most share a common ganglioside co-receptor, GT1b. We determined the crystal structure of the botulinum neurotoxin serotype A binding domain (residues 873-1297) alone and in complex with a GT1b analog at 1.7 A and 1.6 A, respectively. The ganglioside GT1b forms several key hydrogen bonds to conserved residues and binds in a shallow groove lined by Tryptophan 1266. GT1b binding does not induce any large structural changes in the toxin; therefore, it is unlikely that allosteric effects play a major role in the dual receptor recognition. Together with the previously published structures of botulinum neurotoxin serotype B in complex with its protein co-receptor, we can now generate a detailed model of botulinum neurotoxin's interaction with the neuronal cell surface. The two branches of the GT1b polysaccharide, together with the protein receptor site, impose strict geometric constraints on the mode of interaction with the membrane surface and strongly support a model where one end of the 100 A long translocation domain helix bundle swing into contact with the membrane, initiating the membrane anchoring event.PLoS Pathogens 09/2008; 4(8):e1000129. · 9.13 Impact Factor
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ABSTRACT: Botulinum neurotoxins (BoNTs) include seven bacterial toxins (BoNT/A-G) that target presynaptic terminals and act as proteases cleaving proteins required for synaptic vesicle exocytosis. Here we identified synaptic vesicle protein SV2 as the protein receptor for BoNT/D. BoNT/D enters cultured hippocampal neurons via synaptic vesicle recycling and can bind SV2 in brain detergent extracts. BoNT/D failed to bind and enter neurons lacking SV2, which can be rescued by expressing one of the three SV2 isoforms (SV2A/B/C). Localization of SV2 on plasma membranes mediated BoNT/D binding in both neurons and HEK293 cells. Furthermore, chimeric receptors containing the binding sites for BoNT/A and E, two other BoNTs that use SV2 as receptors, failed to mediate the entry of BoNT/D suggesting that BoNT/D binds SV2 via a mechanism distinct from BoNT/A and E. Finally, we demonstrated that gangliosides are essential for the binding and entry of BoNT/D into neurons and for its toxicity in vivo, supporting a double-receptor model for this toxin.PLoS Pathogens 03/2011; 7(3):e1002008. · 9.13 Impact Factor
Article: Bacterial toxins and the nervous system: neurotoxins and multipotential toxins interacting with neuronal cells.[show abstract] [hide abstract]
ABSTRACT: Toxins are potent molecules used by various bacteria to interact with a host organism. Some of them specifically act on neuronal cells (clostridial neurotoxins) leading to characteristics neurological affections. But many other toxins are multifunctional and recognize a wider range of cell types including neuronal cells. Various enterotoxins interact with the enteric nervous system, for example by stimulating afferent neurons or inducing neurotransmitter release from enterochromaffin cells which result either in vomiting, in amplification of the diarrhea, or in intestinal inflammation process. Other toxins can pass the blood brain barrier and directly act on specific neurons.Toxins. 04/2010; 2(4):683-737.