Radman Katarina, Crnolatac Ivo, Bregović Nikola, Matošević Zoe Jelić, Fernandes Pedro A, Merunka Dalibor, Žilić Dijana, Piantanida Ivo, Ašler Ivana Leščić, Bertoša Branimir
Department of Chemistry, Faculty of Science, University of Zagreb, Horvatovac 102a, 10000 Zagreb, Croatia.
Division of Organic Chemistry & Biochemistry, Ruđer Bošković Institute, 10000 Zagreb, Croatia.
Int J Biol Macromol. 2025 Feb;290:138828. doi: 10.1016/j.ijbiomac.2024.138828. Epub 2024 Dec 17.
Streptococcus mutans, a bacterium commonly found in the human oral cavity, is considered the primary causative agent of dental caries. A key player in the pathophysiology of S. mutans is SloR, a 25-kDa metalloregulatory protein. SloR plays a crucial role in coordinating the uptake of essential metal ions, particularly manganese, with the transcription of the bacterium's virulence genes. To elucidate the molecular mechanism underlying the enhanced binding affinity of SloR to DNA upon Mn ion binding, a combination of computational (QM and MD) and experimental (ITC, DSC, CD, EPR) methods have been employed. Computational simulations revealed that Mn binding induces a conformational change of SloR, primarily affecting the positioning of its DNA-binding domains, bringing them to an appropriate position for DNA binding. Consequently, the protein's DNA binding affinity is modulated. Additionally, experimental findings indicate that the SloR monomer binds up to three Mn ions and that the thermodynamic stability of SloR increases upon Mn complexation. The presented computational results also suggest that Mn binding at the primary binding sites is sufficient to trigger the observed conformational change in SloR.
变形链球菌是一种常见于人类口腔中的细菌，被认为是龋齿的主要致病因素。变形链球菌病理生理学中的一个关键因素是SloR，一种25千道尔顿的金属调节蛋白。SloR在协调必需金属离子（特别是锰）的摄取与细菌毒力基因的转录方面发挥着关键作用。为了阐明Mn离子结合后SloR与DNA结合亲和力增强的分子机制，采用了计算（量子力学和分子动力学）和实验（等温滴定量热法、差示扫描量热法、圆二色光谱法、电子顺磁共振波谱法）相结合的方法。计算模拟表明，Mn结合诱导了SloR的构象变化，主要影响其DNA结合结构域的定位，使其处于适合DNA结合的位置。因此，蛋白质的DNA结合亲和力得到调节。此外，实验结果表明，SloR单体可结合多达三个Mn离子，并且Mn络合后SloR的热力学稳定性增加。所呈现的计算结果还表明，在主要结合位点的Mn结合足以触发SloR中观察到的构象变化。
