Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 2, Milan 20126, Italy.
AFFINImeter Scientific & Development team, Software 4 Science Developments, University of Santiago de Compostela, Santiago de Compostela 15782, Spain.
J Am Chem Soc. 2024 Oct 9;146(40):27755-27769. doi: 10.1021/jacs.4c09732. Epub 2024 Sep 30.
Human osteocalcin (OC) undergoes reversible, vitamin K-dependent γ-carboxylation at three glutamic acid residues, modulating its release from bones and its hormonal roles. A complete understanding of OC roles and structure-activity relationships is still lacking, as only uncarboxylated and few differently carboxylated variants have been considered so far. To fill this lack of knowledge, a comprehensive experimental and computational investigation of the structural properties and calcium-binding activity of all the OC variants is reported here. Such a comparative study indicates that the carboxylation sites are not equivalent and differently affect the OC structure and interaction with calcium, properties that are relevant for the modulation of OC functions. This study also discloses cooperative effects and provides structural and mechanistic interpretation. The disclosed peculiar features of each carboxylated proteoform strongly suggest that considering all eight possible OC variants in future studies may help rationalize some of the conflicting hypotheses observed in the literature.
人骨钙素 (OC) 在三个谷氨酸残基上经历维生素 K 依赖性的可逆 γ-羧化，调节其从骨骼中的释放及其激素作用。由于迄今为止仅考虑了未羧化和少数不同羧化的变体，因此对 OC 作用和结构-活性关系的全面了解仍然不足。为了弥补这一知识空白，本文对所有 OC 变体的结构特性和钙结合活性进行了全面的实验和计算研究。这种比较研究表明，羧化位点并不等同，并且会以不同的方式影响 OC 的结构和与钙的相互作用，这些性质与 OC 功能的调节有关。这项研究还揭示了协同效应，并提供了结构和机制解释。所揭示的每种羧化蛋白形式的特殊特征强烈表明，在未来的研究中考虑所有八种可能的 OC 变体可能有助于使文献中观察到的一些相互矛盾的假设合理化。
