title: Split-inteins for simultaneous, site-specific conjugation of quantum dots to multiple protein targets in vivo.
abstract: BACKGROUND
  Proteins labelled with Quantum Dots (QDs) can be imaged over long periods of time with ultrahigh spatial and temporal resolution, yielding important information on the spatiotemporal dynamics of proteins within live cells or in vivo. However one of the major problems regarding the use of QDs for biological imaging is the difficulty of targeting QDs onto proteins. We have recently developed a DnaE split intein-based method to conjugate Quantum Dots (QDs) to the C-terminus of target proteins in vivo. In this study, we expand this approach to achieve site-specific conjugation of QDs to two or more proteins simultaneously with spectrally distinguishable QDs for multiparameter imaging of cellular functions.
  
  
  RESULTS
  Using the DnaE split intein we target QDs to the C-terminus of paxillin and show that paxillin-QD conjugates become localized at focal adhesions allowing imaging of the formation and dissolution of these complexes. We go on to utilize a different split intein, namely Ssp DnaB mini-intein, to demonstrate N-terminal protein tagging with QDs. Combination of these two intein systems allowed us to simultaneously target two distinct proteins with spectrally distinguishable QDs, in vivo, without any cross talk between the two intein systems.
  
  
  CONCLUSIONS
  Multiple target labeling is a unique feature of the intein based methodology which sets it apart from existing tagging methodologies in that, given the large number of characterized split inteins, the number of individual targets that can be simultaneously tagged is only limited by the number of QDs that can be spectrally distinguished within the cell. Therefore, the intein-mediated approach for simultaneous, in vivo, site-specific (N- and C-terminus) conjugation of Quantum Dots to multiple protein targets opens up new possibilities for bioimaging applications and offers an effective system to target QDs and other nanostructures to intracellular compartments as well as specific molecular complexes.
authors.affiliation: Department of Biological Sciences, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus.
authors.forename: Anna
authors.initials: A
authors.lastname: Charalambous
authors.forename: Ioanna
authors.initials: I
authors.lastname: Antoniades
authors.forename: Neophytos
authors.initials: N
authors.lastname: Christodoulou
authors.forename: Paris A
authors.initials: PA
authors.lastname: Skourides
mesh_terms: D000818:Animals; D004258:DNA Polymerase III / Q000235:genetics / Q000378:metabolism; D053488:DnaB Helicases / Q000235:genetics / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000201:enzymology / Q000378:metabolism; D022001:Focal Adhesions / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D047668:Inteins; D051419:Paxillin / Q000235:genetics / Q000378:metabolism; D019154:Protein Splicing; D045663:Quantum Dots; D012313:RNA / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014981:Xenopus / Q000196:embryology; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D051419:Paxillin; D011993:Recombinant Fusion Proteins; D029867:Xenopus Proteins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D012313:RNA; C074904:DNA polymerase III, alpha subunit; D004258:DNA Polymerase III; D053488:DnaB Helicases