title: Structure and dynamics of the integrin LFA-1 I-domain in the inactive state underlie its inside-out/outside-in signaling and allosteric mechanisms.
abstract: Lymphocyte function-associated antigen 1 (LFA-1) is an integrin that transmits information in two directions across the plasma membrane of leukocytes, in so-called outside-in and inside-out signaling mechanisms. To investigate the structural basis of these mechanisms, we studied the conformational space of the apo I-domain using replica-averaged metadynamics simulations in combination with nuclear magnetic resonance chemical shifts. We thus obtained a free energy landscape that reveals the existence of three conformational substates of this domain. The three substates include conformations similar to existing crystallographic structures of the low-affinity I-domain, the inactive I-domain with an allosteric antagonist inhibitor bound underneath α helix 7, and an intermediate affinity state of the I-domain. The multiple substates were validated with residual dipolar coupling measurements. These results suggest that the presence of three substates in the apo I-domain enables the precise regulation of the binding process that is essential for the physiological function of LFA-1.
authors.affiliation: Department of Chemistry, Lensfield Road, University of Cambridge, Cambridge CB2 1EW, UK.
authors.forename: Predrag
authors.initials: P
authors.lastname: Kukic
authors.affiliation: Department of Chemistry, Lensfield Road, University of Cambridge, Cambridge CB2 1EW, UK; Biozentrum, University of Basel, Klingelbergstrasse 50/70, Basel 4056, Switzerland.
authors.forename: Hoi Tik
authors.initials: HT
authors.lastname: Alvin Leung
authors.affiliation: Department of Chemistry, Lensfield Road, University of Cambridge, Cambridge CB2 1EW, UK; Dipartimento di Scienze Biomediche Sperimentali e Cliniche, Università degli Studi di Firenze, Viale G. B. Morgagni 50, 50134, Firenze, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Bemporad
authors.affiliation: Department of Chemistry, Lensfield Road, University of Cambridge, Cambridge CB2 1EW, UK.
authors.forename: Francesco A
authors.initials: FA
authors.lastname: Aprile
authors.affiliation: Department of Chemistry, Lensfield Road, University of Cambridge, Cambridge CB2 1EW, UK.
authors.forename: Janet R
authors.initials: JR
authors.lastname: Kumita
authors.affiliation: Division of Molecular Biosciences, Imperial College London, London SW7 2AZ, UK.
authors.forename: Alfonso
authors.initials: A
authors.lastname: De Simone
authors.affiliation: Department of Chemistry, Lensfield Road, University of Cambridge, Cambridge CB2 1EW, UK.
authors.forename: Carlo
authors.initials: C
authors.lastname: Camilloni
authors.affiliation: Department of Chemistry, Lensfield Road, University of Cambridge, Cambridge CB2 1EW, UK. Electronic address: mv245@cam.ac.uk.
authors.forename: Michele
authors.initials: M
authors.lastname: Vendruscolo
mesh_terms: D000494:Allosteric Regulation; D000595:Amino Acid Sequence; D016169:Lymphocyte Function-Associated Antigen-1 / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D015398:Signal Transduction
chemical_list: D016169:Lymphocyte Function-Associated Antigen-1