1
|
Ng YK, Konermann L. Mechanism of Protein Aggregation Inhibition by Arginine: Blockage of Anionic Side Chains Favors Unproductive Encounter Complexes. J Am Chem Soc 2024; 146:8394-8406. [PMID: 38477601 DOI: 10.1021/jacs.3c14180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/14/2024]
Abstract
Aggregation refers to the assembly of proteins into nonphysiological higher order structures. While amyloid has been studied extensively, much less is known about amorphous aggregation, a process that interferes with protein expression and storage. Free arginine (Arg+) is a widely used aggregation inhibitor, but its mechanism remains elusive. Focusing on myoglobin (Mb), we recently applied atomistic molecular dynamics (MD) simulations for gaining detailed insights into amorphous aggregation (Ng J. Phys. Chem. B 2021, 125, 13099). Building on that approach, the current work for the first time demonstrates that MD simulations can directly elucidate aggregation inhibition mechanisms. Comparative simulations with and without Arg+ reproduced the experimental finding that Arg+ significantly decreased the Mb aggregation propensity. Our data reveal that, without Arg+, protein-protein encounter complexes readily form salt bridges and hydrophobic contacts, culminating in firmly linked dimeric aggregation nuclei. Arg+ promotes the dissociation of encounter complexes. These "unproductive" encounter complexes are favored because Arg+ binding to D- and E- lowers the tendency of these anionic residues to form interprotein salt bridges. Side chain blockage is mediated largely by the guanidinium group of Arg+, which binds carboxylates through H-bond-reinforced ionic contacts. Our MD data revealed Arg+ self-association into a dynamic quasi-infinite network, but we found no evidence that this self-association is important for protein aggregation inhibition. Instead, aggregation inhibition by Arg+ is similar to that mediated by free guanidinium ions. The computational strategy used here should be suitable for the rational design of aggregation inhibitors with enhanced potency.
Collapse
Affiliation(s)
- Yuen Ki Ng
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| |
Collapse
|
2
|
Ma G, Ma S, Du H, Li X, Tao Q, Hu Q, Xiao H. Interactions between intestinal microbial fermentation products of Pleurotus eryngii polysaccharide with gut mucus. Food Funct 2024; 15:1476-1488. [PMID: 38226839 DOI: 10.1039/d3fo04787c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2024]
Abstract
Recently, Pleurotus eryngii (P. eryngii) polysaccharide (PEP) has received a lot of attention from many researchers as the primary active substance. The PEP influences the gut microbiota in several ways, including the interaction of fermentation products with the intestinal mucus layer (IML) and intestinal epithelial cells. Herein, we characterized interactions between the IML and PEP after degradation by the gut microbes. Our results showed that fermented P. eryngii polysaccharide (FPEP) can interact with intestinal mucus (IM), and this interaction can reduce the degree of molecular aggregation of polysaccharides. At the same time, the fermentation time of FPEP also affects the interaction between the two. SEM showed that the FPEP solution tended to aggregate into larger particles, while with the addition of IM, the FPEP molecules were dispersed. Particle size measurements unveil substantial differences in the fermented polysaccharides' particle size between the group with supplementary IM (0 hours of fermentation: 485.1 ± 11.3 nm) and the group without IM (0 hours of fermentation: 989.33 ± 21.3 nm). Remarkably, within the group with added IM, the particle size reached its maximum at 24 hours of fermentation (585.87 ± 42.83 nm). Additionally, turbidity assessments demonstrate that, during the 12-hour interaction period, the 24-hour fermented polysaccharides consistently exhibit the highest OD values, ranging between 0.57 and 0.61. This work investigates the interaction between FPEP and IM, predicting the adhesion of polysaccharides to IM. Meanwhile, this provides a theoretical basis for further studies on the absorption and transport pathways of PEP and provides a novel research viewpoint on intestinal digestion and absorption.
Collapse
Affiliation(s)
- Gaoxing Ma
- Collaborative Innovation Center for Modern Grain Circulation and Safety, Jiangsu Province Engineering Research Center of Edible Fungus Preservation and Intensive Processing, College of Food Science and Engineering, Nanjing University of Finance and Economics, Nanjing 210023, China
| | - Sai Ma
- Collaborative Innovation Center for Modern Grain Circulation and Safety, Jiangsu Province Engineering Research Center of Edible Fungus Preservation and Intensive Processing, College of Food Science and Engineering, Nanjing University of Finance and Economics, Nanjing 210023, China
| | - Hengjun Du
- Department of Food Science, University of Massachusetts, Amherst, MA 01002, USA.
| | - Xinyi Li
- Collaborative Innovation Center for Modern Grain Circulation and Safety, Jiangsu Province Engineering Research Center of Edible Fungus Preservation and Intensive Processing, College of Food Science and Engineering, Nanjing University of Finance and Economics, Nanjing 210023, China
| | - Qi Tao
- Collaborative Innovation Center for Modern Grain Circulation and Safety, Jiangsu Province Engineering Research Center of Edible Fungus Preservation and Intensive Processing, College of Food Science and Engineering, Nanjing University of Finance and Economics, Nanjing 210023, China
| | - Qiuhui Hu
- Collaborative Innovation Center for Modern Grain Circulation and Safety, Jiangsu Province Engineering Research Center of Edible Fungus Preservation and Intensive Processing, College of Food Science and Engineering, Nanjing University of Finance and Economics, Nanjing 210023, China
| | - Hang Xiao
- Department of Food Science, University of Massachusetts, Amherst, MA 01002, USA.
| |
Collapse
|