title: Resolution of sub-nanosecond motions in botulinum neurotoxin endopeptidase: An evidence of internal flexibility.
abstract: Botulinum neurotoxins (BoNTs) are the most poisonous substances known to mankind, which act on the peripheral nervous system leading to flaccid paralysis. Although co-crystal structure of BoNT/A light chain (LC) reveals some unique features of the biological function of this molecule, structural characteristics in solution reveal its dynamic features, not available through the published crystal structures. In this study, we have examined internal flexibility of this molecule by measuring rotational correlation time as a function of viscosity, using frequency domain fluorescence anisotropy decay technique. Fluorescence anisotropy decay of BoNT/A LC resolved sub-nanosecond local motion (faster component), interpreted as internal flexibility of the molecule was affected significantly with viscosity. Both local and global movements were affected by viscosity, which indicates the accessibility of protein core and flexibility of overall structure. In conclusion, this work demonstrates the presence of flexibility in the internal peptide segments, which appears to play a significant role in BoNT/A LC biological function.
authors.affiliation: Botulinum Research Center, Institute of Advanced Sciences, Dartmouth, MA 02747, USA.
authors.forename: Raj
authors.initials: R
authors.lastname: Kumar
authors.affiliation: Department of Chemistry and Biochemistry, University of Massachusetts, Dartmouth, MA 02747, USA.
authors.forename: Shuowei
authors.initials: S
authors.lastname: Cai
authors.affiliation: Department of Chemistry and Biochemistry, University of Massachusetts, Dartmouth, MA 02747, USA.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Ojadi
authors.affiliation: Botulinum Research Center, Institute of Advanced Sciences, Dartmouth, MA 02747, USA. Electronic address: bsingh@inads.org.
authors.forename: Bal R
authors.initials: BR
authors.lastname: Singh
mesh_terms: D001905:Botulinum Toxins / Q000737:chemistry*; D020134:Catalytic Domain; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D005990:Glycerol / Q000737:chemistry; D007700:Kinetics; D009038:Motion; D017510:Protein Folding; D017433:Protein Structure, Secondary; D012399:Rotation; D013050:Spectrometry, Fluorescence; D014783:Viscosity
chemical_list: D001905:Botulinum Toxins; D005990:Glycerol
keywords: Botulinum toxin; Circular dichroism; Fluorescence anisotropy decay; Molten globule; Protein denaturation; Protein flexibility