Calmodulin-binding peptide is a natural peptide aptamer that binds to human midkine in a metal ion-dependent manner
Hidenao Arai1, Haruaki Inoue1, Hiroaki Tomioka2
1Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo Sakura-ku, Saitama, 338-8570, Japan.
Abstract:
Calmodulin-binding peptide (CBP), derived from the calmodulin recognition domain of skeletal muscle myosin light chain kinase, undergoes calcium ion-dependent structural changes. This study reports the discovery that human midkine, which is increasingly recognized as a cancer marker, interacts with CBP. Notably, this interaction occurs in the presence of sodium ions rather than calcium ions. A structural analysis employing the program AlphaFold 3 predicted the interaction of CBP with calmodulin, which consists of α-helices, in the presence of Ca2+. Conversely, surface plasmon resonance experiments revealed that in the presence of Na+ ions, CBP interacts with human midkine, which consists of β-sheets. These results suggest that CBP may function as a natural peptide aptamer, switching its target protein in the presence of different prevailing metal ions.
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