Calmodulin (CaM) is an important Ca2+ sensing protein. Among the high number of target proteins are Munc13, skMLCK, AC1, and AC8. In this work, the interaction between CaM and all these proteins was studied. Munc13 proteins are important presynaptic regulators. It had been found that short Munc13 peptides of all four Munc13 isoforms, representing the minimal CaM-binding sequence, bind with a 1-5-8 CaM-binding motif in an antiparallel manner to CaM. The CaM/Munc13 peptide complexes are similar to the CaM/NO synthase peptide complex, showing a closed conformation of CaM. Although an extended CaM conformation was observed in an NMR structure with C-terminally elongated Munc13 peptides, this extended conformation was not found in the CaM/skMLCK peptide complex after C-terminal elongation and amino acid exchanges of the classical skMLCK peptide. Additionally, deeper insights into the CaM/AC1 and AC8 interaction could be gained by chemical cross-linking and mass spectrometry.