Maurocalcine (MCa) is a 33 mer toxin initially identified from a tunisian scorpion venom, scorpio maurus palmatus. This peptide initially triggered our interest for its pharmacological activity on Ryanodine Receptor type 1 (RyR1) of skeletal muscles. In studying how this toxin reaches the intracellular RyR1, it has been shown that MCa could be placed in the growing family of cell penetrating peptides. Since the discovery that MCa can act as a transport agent for the intracellular delivery of fluorescent streptavidine, data have accumulated to illustrate the amazing biotechnological properties of this toxin. Several new analogs have been produced that keep cell penetration properties and lose pharmacological activity of the native molecule. This is the case for a linear analog of MCa synthesized by replacing internal cysteine residues by aminobutyric acid, or by the synthesis of a MCa analog with all its amino acid in D conformation. MCa proved efficient for the intracellular delivery of nanoparticles leading to a myriad of hi-tech applications. Finally, MCa has been grafted on an anti-tumor agent, doxorubicin, to made chemo-resistant tumor cells chemo-sensitive. So it seems that MCa begins its career as a biotechnological tool, and that this toxin will be helpful to see the light on the mechanistic aspects of RyR function.
