8.B.16 The Membrance-pentitrating, Ryanodine Receptor-activating Maurocalcine (MaCa) Family

Maurocalcine (maurocalcin) (MCa) is a 33-amino acid residue peptide that was initially identified in the Tunisian scorpion, Scorpion maurus palmatus. This peptide triggers interest for three main reasons. First, it helps unravelling the mechanistic basis of Ca²⁺ mobilization from the sarcoplasmic reticulus because of its sequence homology with a calcium channel domain in excitation-contraction coupling. Second, it shows potent pharmacological properties because of its ability to activate the ryanodine receptor. Finally, it is of technological value because of its ability to carry cell-impermeable compounds across the plasma membrane. Mabrouk et al., 2007 characterized the molecular determinants that underlie the pharmacological and cell-penetrating properties of maurocalcin. They identify several key amino acid residues of the peptide that determine cell penetrability. Basic amino acid residues are required for an interaction with negatively charged lipids of the plasma membrane. Maurocalcine analogues that penetrate better have stronger interactions with negatively charged lipids.