Análisis de la Interfaz de interacción de la Calmodulina con su dominio de unión en las isoformas de Ca2+-ATPsas de membrana plasmática en humano

Abstract

Intracellular calcium (Ca²⁺) plays a key role as a second messenger in numerous physiological processes; therefore, its precise regulation is essential to prevent cellular toxicity. Plasma membrane Ca²⁺-ATPases (PMCAs) are central to this regulation and are functionally modulated through their interaction with calmodulin (CaM). This study characterizes the CaM–PMCA interaction interface across different human isoforms, evaluating both previously described mutations (G→D, V→F, W→A) and novel point mutations (R→S, F→L) located within the calmodulin-binding domain (CaMBD). Isoforms and splice variants were retrieved from GenBank, and the CaMBD structures were modeled using AlphaFold and PEP-FOLD4. Molecular docking was performed using the 2kne structure as a reference, and binding free energy values (ΔG) were calculated using FoldX. Known mutations associated with pathology showed a significant decrease in CaM–PMCA complex stability, validating the sensitivity of the modeling system. Novel mutations also produced relevant changes in CaM binding affinity, particularly R→S in PMCA1a and PMCA4b, and F→L in PMCA3a, suggesting their potential to disrupt calcium transport regulation in sensitive tissues such as the nervous or muscular systems. The generated models reveal that local differences in CaMBD across isoforms impact their susceptibility to point mutations, allowing differential predictions of binding behavior. This robust methodological approach combines structural modeling, molecular docking, and energetic calculations to anticipate alterations in PMCA function that may lead to cellular or systemic dysfunction. These findings offer important insights into the structural and functional consequences of PMCA mutations in the context of Ca²⁺ homeostasis and human disease.