Lymphocyte function-associated antigen-1 (LFA-1) is an integrin protein that transmits information across the plasma membrane through the so-called inside-out and outside-in signaling mechanisms. To investigate these mechanisms, we carried out an NMR analysis of the dynamics of the LFA-1 I-domain, which has enabled us to characterize the motions of this domain on a broad range of timescales. We studied first the internal motions on the nanosecond timescale by spin relaxation measurements and model-free analysis. We then extended this analysis to the millisecond timescale motions by measuring <sup>15</sup>N-<sup>1</sup>H residual dipolar couplings of the backbone amide groups. We analyzed these results in the context of the three major conformational states of the I-domain using their corresponding X-ray crystallographic structures. Our results highlight the importance of the low-frequency motions of the LFA-1 I-domain in the inactive apo-state. We found in particular that α-helix 7 is in a position in the apo-closed state that cannot be fully described by any of the existing X-ray structures, as it appears to be in dynamic exchange between different conformations. This type of motion seems to represent an inherent property of the LFA-1 I-domain and might be relevant for controlling the access to the allosteric binding pocket, as well as for the downward displacement of α-helix 7 that is required for the activation of LFA-1.
|Titolo:||NMR characterization of the conformational fluctuations of the human lymphocyte function-associated antigen-1 I-domain|
|Parole Chiave:||allostery; NMR spectroscopy; protein dynamics; signaling mechanism; Humans; Lymphocyte Function-Associated Antigen-1; Models, Molecular; Nuclear Magnetic Resonance, Biomolecular; Protein Conformation; Biochemistry; Molecular Biology; Medicine (all)|
|Settore Scientifico Disciplinare:||Settore FIS/07 - Fisica Applicata(Beni Culturali, Ambientali, Biol.e Medicin)|
|Data di pubblicazione:||2014|
|Digital Object Identifier (DOI):||10.1002/pro.2538|
|Appare nelle tipologie:||01 - Articolo su periodico|