title: The motion of a single molecule, the lambda-receptor, in the bacterial outer membrane.
abstract: Using optical tweezers and single particle tracking, we have revealed the motion of a single protein, the lambda-receptor, in the outer membrane of living Escherichia coli bacteria. We genetically modified the lambda-receptor placing a biotin on an extracellular site of the receptor in vivo. The efficiency of this in vivo biotinylation is very low, thus enabling the attachment of a streptavidin-coated bead binding specifically to a single biotinylated lambda-receptor. The bead was used as a handle for the optical tweezers and as a marker for the single particle tracking routine. We propose a model that allows extraction of the motion of the protein from measurements of the mobility of the bead-molecule complex; these results are equally applicable to analyze bead-protein complexes in other membrane systems. Within a domain of radius approximately 25 nm, the receptor diffuses with a diffusion constant of (1.5 +/- 1.0) x 10(-9) cm(2)/s and sits in a harmonic potential as if it were tethered by an elastic spring of spring constant of ~1.0 x 10(-2) pN/nm to the bacterial membrane. The purpose of the protein motion might be to facilitate transport of maltodextrins through the outer bacterial membrane.
authors.affiliation: The Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, 2100 Copenhagen Ø, Denmark. oddershede@nbi.dk
authors.forename: Lene
authors.initials: L
authors.lastname: Oddershede
authors.forename: Jakob Kisbye
authors.initials: JK
authors.lastname: Dreyer
authors.forename: Sonia
authors.initials: S
authors.lastname: Grego
authors.forename: Stanley
authors.initials: S
authors.lastname: Brown
authors.forename: Kirstine
authors.initials: K
authors.lastname: Berg-Sørensen
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000502:physiology*; D001710:Biotin / Q000737:chemistry / Q000235:genetics; D019921:Biotinylation / Q000379:methods; D003198:Computer Simulation; D004548:Elasticity; D004926:Escherichia coli / Q000737:chemistry / Q000502:physiology* / Q000648:ultrastructure; D007834:Lasers; D008846:Micromanipulation / Q000295:instrumentation / Q000379:methods; D008863:Microspheres; D008954:Models, Biological; D008956:Models, Chemical; D009038:Motion; D036103:Nanotechnology / Q000295:instrumentation / Q000379:methods; D055095:Optics and Photonics / Q000295:instrumentation; D010316:Particle Size; D018272:Porins; D011487:Protein Conformation; D011991:Receptors, Virus / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D019809:Streptavidin / Q000737:chemistry; D013314:Stress, Mechanical
chemical_list: D001425:Bacterial Outer Membrane Proteins; D018272:Porins; D011991:Receptors, Virus; D011994:Recombinant Proteins; C016532:maltoporins; D001710:Biotin; D019809:Streptavidin