Structural insights into calmodulin/Munc13 interaction.

Munc13 proteins are essential presynaptic regulators that mediate synaptic vesicle priming and play a role in the regulation of neuronal short-term synaptic plasticity. All four Munc13 isoforms share a common domain structure, including a calmodulin (CaM) binding site in their otherwise divergent N-termini. Here, we summarize recent results on the investigation of the CaM/Munc13 interaction. By combining chemical cross-linking, photoaffinity labeling, and mass spectrometry, we showed that all neuronal Munc13 isoforms exhibit similar CaM binding modes. Moreover, we demonstrated that the 1-5-8-26 CaM binding motif discovered in Munc13-1 cannot be induced in the classical CaM target skMLCK, indicating unique features of the Munc13 CaM binding motif.