Somarathne Radha P, Misra Sandeep K, Kariyawasam Chathuri S, Kessl Jacques J, Sharp Joshua S, Fitzkee Nicholas C
Department of Chemistry, Mississippi State University, Mississippi State, MS 39762.
Department of BioMolecular Sciences, University of Mississippi, University, MS 38677.
bioRxiv. 2023 Sep 19:2023.08.28.554951. doi: 10.1101/2023.08.28.554951.
In biological systems, proteins can bind to nanoparticles to form a "corona" of adsorbed molecules. The nanoparticle corona is of high interest because it impacts the organism's response to the nanomaterial. Understanding the corona requires knowledge of protein structure, orientation, and dynamics at the surface. Ultimately, a residue-level mapping of protein behavior on nanoparticle surfaces is needed, but this mapping is difficult to obtain with traditional approaches. Here, we have investigated the interaction between R2ab and polystyrene nanoparticles (PSNPs) at the level of individual residues. R2ab is a bacterial surface protein from and is known to interact strongly with polystyrene, leading to biofilm formation. We have used mass spectrometry after lysine methylation and hydrogen-deuterium exchange (HDX) NMR spectroscopy to understand how the R2ab protein interacts with PSNPs of different sizes. Through lysine methylation, we observe subtle but statistically significant changes in methylation patterns in the presence of PSNPs, indicating altered protein surface accessibility. HDX measurements reveal that certain regions of the R2ab protein undergo faster exchange rates in the presence of PSNPs, suggesting conformational changes upon binding. Both results support a recently proposed "adsorbotope" model, wherein adsorbed proteins consist of unfolded anchor points interspersed with regions of partial structure. Our data also highlight the challenges of characterizing complex protein-nanoparticle interactions using these techniques, such as fast exchange rates. While providing insights into how proteins respond to nanoparticle surfaces, this research emphasizes the need for advanced methods to comprehend these intricate interactions fully at the residue level.
在生物系统中，蛋白质可与纳米颗粒结合，形成一层由吸附分子构成的“冠层”。纳米颗粒冠层备受关注，因为它会影响生物体对纳米材料的反应。要了解冠层，需要掌握蛋白质在表面的结构、取向和动力学知识。最终，需要对纳米颗粒表面蛋白质行为进行残基水平的图谱绘制，但用传统方法很难获得这样的图谱。在此，我们在单个残基水平上研究了R2ab与聚苯乙烯纳米颗粒（PSNPs）之间的相互作用。R2ab是一种来自[具体来源未提及]的细菌表面蛋白，已知它与聚苯乙烯有强烈相互作用，会导致生物膜形成。我们使用赖氨酸甲基化后的质谱分析和氢氘交换（HDX）核磁共振光谱来了解R2ab蛋白如何与不同大小的PSNPs相互作用。通过赖氨酸甲基化，我们观察到在有PSNPs存在时甲基化模式有细微但具有统计学意义的变化，这表明蛋白质表面可及性发生了改变。HDX测量结果显示，在有PSNPs存在时，R2ab蛋白的某些区域交换速率加快，这表明结合时发生了构象变化。这两个结果都支持了最近提出的“吸附表位”模型，即吸附的蛋白质由散布着部分结构区域的未折叠锚定点组成。我们的数据还凸显了使用这些技术表征复杂的蛋白质 - 纳米颗粒相互作用所面临的挑战，比如快速交换速率。在深入了解蛋白质对纳米颗粒表面的反应的同时，这项研究强调需要先进方法来在残基水平上全面理解这些复杂的相互作用。
