title: Tandem fluorescent proteins as enhanced FRET-based substrates for botulinum neurotoxin activity.
abstract: The light chain of botulinum neurotoxin A (BoNT/A-LC) is a zinc-metalloprotease that requires two extended exosites for optimal substrate binding and recognition of its intracellular target SNAP25. CFP and YFP connected through SNAP25 peptide (141-206) containing both exosites (CsY) has been used in a FRET-based assay for BoNT/A. To further improve the FRET efficiency in this BoNT/A substrate for in vitro high-throughput assays, we explored the feasibility of enhancing the capture of CFP emission by doubling the number of YFP acceptors. In comparison to CsY, the tandem fluorescence substrates CsYY and YsCsY enhanced the ratiometric fluorescence signal between YFP and CFP. YsCsY, containing two substrate sites, offered the greatest fluorometric change upon toxin-catalyzed cleavage. In addition to known approaches for enhancing fluorescence yield through various mutations, this alternative tandem substrate approach can boost the FRET signal and is particularly useful for substrates requiring extensive exosite recognition for specificity.
authors.affiliation: Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Melissa
authors.initials: M
authors.lastname: Pires-Alves
authors.forename: Mengfei
authors.initials: M
authors.lastname: Ho
authors.forename: Karla K
authors.initials: KK
authors.lastname: Aberle
authors.forename: Kim D
authors.initials: KD
authors.lastname: Janda
authors.forename: Brenda A
authors.initials: BA
authors.lastname: Wilson
mesh_terms: D019274:Botulinum Toxins, Type A / Q000737:chemistry*; D031541:Fluorescence Resonance Energy Transfer; D008164:Luminescent Proteins / Q000737:chemistry*; D050825:Synaptosomal-Associated Protein 25 / Q000737:chemistry; D013696:Temperature; D015032:Zinc / Q000737:chemistry
chemical_list: D008164:Luminescent Proteins; D050825:Synaptosomal-Associated Protein 25; D019274:Botulinum Toxins, Type A; D015032:Zinc