title: Real-time transmembrane translocation of penetratin driven by light-generated proton pumping.
abstract: Cell penetrating peptides (CPPs) are small peptides that are able to penetrate the plasma membrane of mammalian cells. Because these peptides can also carry large hydrophilic cargos such as proteins, they could potentially be used to transport biologically active drugs across cell membranes to modulate in vivo biology. One characteristic feature of the CPPs is that they typically have a net positive charge. Therefore, a key issue associated with the transport mechanism is the role of the transmembrane electrochemical potential in driving the peptides across the membrane. In this study, we have reconstituted bacteriorhodopsin (bR) in large unilamellar vesicles (LUVs) with fluorescein-labeled CPP penetratin enclosed within the LUVs under conditions when the fluorescence is quenched. Illumination of the bacteriorhodopsin-containing LUVs resulted in creation of a transmembrane proton electrochemical gradient (positive on the inside). Upon generation of this gradient, an increase in fluorescence was observed, which shows that the proton gradient drives the translocation of penetratin. The mechanism most likely can be generalized to other CPPs.
authors.affiliation: Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden.
authors.forename: Jörgen
authors.initials: J
authors.lastname: Björklund
authors.forename: Henrik
authors.initials: H
authors.lastname: Biverståhl
authors.forename: Astrid
authors.initials: A
authors.lastname: Gräslund
authors.forename: Lena
authors.initials: L
authors.lastname: Mäler
authors.forename: Peter
authors.initials: P
authors.lastname: Brzezinski
mesh_terms: D001436:Bacteriorhodopsins / Q000502:physiology* / Q000528:radiation effects; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000502:physiology* / Q000528:radiation effects; D057846:Cell-Penetrating Peptides; D003199:Computer Systems; D008027:Light; D010455:Peptides / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology*; D017494:Proton Pumps / Q000502:physiology*
chemical_list: D002352:Carrier Proteins; D057846:Cell-Penetrating Peptides; D010455:Peptides; D017494:Proton Pumps; D001436:Bacteriorhodopsins; C414409:penetratin