Kumar Sanjay, Prabhu N Prakash
Department of Biotechnology and Bioinformatics, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India.
ACS Omega. 2025 Jun 16;10(25):26935-26952. doi: 10.1021/acsomega.5c01998. eCollection 2025 Jul 1.
In protein-surfactant interactions, the alkyl chain length of surfactants and the surface-exposed residues of proteins play essential roles in binding and unfolding. To investigate this, the interactions of sodium octyl (SOS), decyl (SDeS), and dodecyl (SDoS) sulfates were studied with native and partially unfolded forms of ribonuclease A (ox-RNase A and rd-RNase A) by using surface plasmon resonance (SPR), optical spectroscopy, and molecular dynamics (MD) simulations. rd-RNase A was obtained by partial reduction of the disulfide bonds of RNase A. MD simulations of RNase A in its native and unfolded states were carried out in the presence of all three surfactants in their monomeric and micellar concentrations, respectively. The binding affinity of surfactants differs between ox-RNase A and rd-RNase A. Monomeric forms of the surfactants do not affect the structure and stability of either form of RNase A. Upon micelle formation of the surfactants, ox-RNase A loses its tertiary interactions along with β-sheets. However, it forms non-native α-helices that gradually destabilize ox-RNase A. rd-RNase A initially forms more β-sheets, which stabilize the protein. Further increases in surfactant concentrations destabilize the β-sheets and induce the formation of non-native α-helices. MD simulation results suggest that rd-RNase A induces micelle formation with higher aggregation numbers than ox-RNase A. At monomeric concentrations, the interactions of surfactants could be predominantly ionic, whereas at micellar concentrations, hydrophobic interactions contribute significantly. The exposed hydrophobic surfaces of partially unfolded rd-RNase A facilitate binding of the surfactant to the protein. This results in differences in the unfolding pathways of rd-RNase A and ox-RNase A.
在蛋白质与表面活性剂的相互作用中，表面活性剂的烷基链长度以及蛋白质表面暴露的残基在结合和去折叠过程中起着至关重要的作用。为了对此进行研究，通过表面等离子体共振（SPR）、光谱学和分子动力学（MD）模拟，研究了辛基硫酸钠（SOS）、癸基硫酸钠（SDeS）和十二烷基硫酸钠（SDoS）与天然形式和部分去折叠形式的核糖核酸酶A（氧化型核糖核酸酶A和还原型核糖核酸酶A）之间的相互作用。还原型核糖核酸酶A是通过部分还原核糖核酸酶A的二硫键获得的。分别在三种表面活性剂的单体浓度和胶束浓度存在的情况下，对处于天然状态和去折叠状态的核糖核酸酶A进行了MD模拟。氧化型核糖核酸酶A和还原型核糖核酸酶A对表面活性剂的结合亲和力有所不同。表面活性剂的单体形式不会影响任何一种形式的核糖核酸酶A的结构和稳定性。随着表面活性剂形成胶束，氧化型核糖核酸酶A失去其三级相互作用以及β折叠。然而，它形成了非天然的α螺旋，这逐渐使氧化型核糖核酸酶A不稳定。还原型核糖核酸酶A最初形成更多的β折叠，从而稳定了蛋白质。表面活性剂浓度的进一步增加会使β折叠不稳定，并诱导形成非天然的α螺旋。MD模拟结果表明，还原型核糖核酸酶A诱导形成的胶束聚集数比氧化型核糖核酸酶A更高。在单体浓度下，表面活性剂的相互作用可能主要是离子性的，而在胶束浓度下，疏水相互作用起显著作用。部分去折叠的还原型核糖核酸酶A暴露的疏水表面促进了表面活性剂与蛋白质的结合。这导致了还原型核糖核酸酶A和氧化型核糖核酸酶A去折叠途径的差异。
