Characterisation of the conformational preference and dynamics of the intrinsically disordered N-terminal region of Beclin 1 by NMR spectroscopy

• Detailed characterisation of the Beclin 1 N-terminal domain by NMR
• The BH3 domain shows little conformational preference.
• Beclin1 N-terminal domain is highly dynamic at ps–ns timescale.
• BH3 helix formed upon binding Bcl-2 is likely induced rather than pre-existing.

Beclin 1 is a 450 amino acid protein that plays critical roles in the early stages of autophagosome formation. We recently reported the successful expression, purification and structural characterisation of the entire N-terminal region of Beclin 1 (residues 1–150), including its backbone NMR chemical shift assignments. Based on assigned backbone NMR chemical shifts, it has been established that the N-terminal region of Beclin 1 (1–150), including the BH3 domain (112 − 123), is intrinsically disordered in the absence of its interaction partners. Here, a detailed study of its conformational preference and backbone dynamics obtained from an analysis of its secondary structure populations using the δ2D method, and the measurements of effective hydrodynamic radius as well as 1H temperature coefficients, 1H solvent exchange rates, and 15N relaxation parameters of backbone amides using NMR spectroscopy is reported. These data provide further evidence for the intrinsically disordered nature of the N-terminal region of Beclin 1 and support the view that the helical conformation adopted by the Beclin 1 BH3 domain upon interaction with binding partners such as BCL-2 pro-survival proteins is likely induced rather than pre-existing.

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