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Updated: Apr 25, 2026
From a 2DE-Gel Spot to Protein Function: Lesson Learned From HS1 in Chronic Lymphocytic Leukemia
Published on: October 19, 2014
NMR characterization of the conformational fluctuations of the human lymphocyte function-associated antigen-1
Hoi Tik Alvin Leung1, Predrag Kukic, Carlo Camilloni
1Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, United Kingdom; Biozentrum, University of Basel, Basel, CH-4056, Switzerland.
Insights
Nuclear magnetic resonance (NMR) reveals crucial dynamics of the Lymphocyte function-associated antigen-1 (LFA-1) I-domain. These motions, particularly in the inactive state, are key to LFA-1
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Biophysics
Background:
- Lymphocyte function-associated antigen-1 (LFA-1) is an integrin crucial for immune cell interactions.
- LFA-1 mediates signaling through inside-out and outside-in pathways.
- Understanding LFA-1 I-domain dynamics is vital for deciphering its regulatory mechanisms.
Purpose of the Study:
- To investigate the dynamics of the LFA-1 I-domain across various timescales.
- To characterize the motions relevant to LFA-1's signaling functions.
- To correlate observed dynamics with known conformational states.
Main Methods:
- Nuclear Magnetic Resonance (NMR) spectroscopy was employed.
- Spin relaxation measurements and model-free analysis characterized nanosecond timescale motions.
- Residual dipolar couplings measured millisecond timescale motions.
Main Results:
- Low-frequency motions of the LFA-1 I-domain in the inactive apo-state were highlighted.
- Alpha-helix 7 exhibits dynamic conformational exchange in the apo-closed state, not fully captured by X-ray structures.
- These inherent motions may regulate allosteric binding pocket access and activation.
Conclusions:
- The LFA-1 I-domain possesses inherent dynamic properties crucial for its function.
- Dynamic exchange of alpha-helix 7 is a key feature of the inactive state.
- These findings provide insights into LFA-1 activation mechanisms and allosteric regulation.
Abstract:
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 (15) N-(1) 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.
