Binary-FRET reveals transient excited-state structure associated with activity-dependent CaMKII - NR2B binding and...

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• Synaptic functions rely on intricate protein dynamics and interactions influenced by intracellular calcium.
• Studying these dynamics requires methods capable of monitoring conformational changes and protein-protein interactions simultaneously under physiological conditions.

Purpose of the Study:

• To investigate the dynamics of calcium-calmodulin dependent protein kinase-II (CaMKII) holoenzyme catalytic-domain pair separation.
• To elucidate the role of CaMKII in activity-dependent holoenzyme affinity for the NR2B binding fragment of the N-methyl-D-aspartate receptor.
• To explore calcium-dependent adaptation in T-site ligand binding affinity.

Main Methods:

• Utilized time-lapse Förster resonance energy transfer (FRET) to multiplex two energy transfer reactions.
• Developed and applied the Binary-FRET technique to independently monitor CaMKII holoenzyme dynamics.
• Investigated protein dynamics at non-saturating free calcium concentrations.

Main Results:

• Identified a transient excited-state intermediate in the CaMKII holoenzyme where catalytic domains separate before NR2B association.
• Demonstrated that CaMKII holoenzyme exhibits calcium-dependent adaptation of T-site ligand binding affinity at non-saturating calcium levels.
• Showcased the ability of multiplexed FRET to reveal biochemical plasticity in protein complexes.

Conclusions:

• The findings reveal a novel intermediate state in CaMKII activation, crucial for understanding synaptic plasticity.
• The study highlights the adaptive nature of CaMKII binding affinity in response to fluctuating intracellular calcium concentrations.
• Multiplexed FRET is a powerful tool for dissecting complex protein dynamics in response to physiological stimuli.