Three Ways For Protein Aggregation and The Control Strategies

Background

Protein aggregation is a critical issue in biomedical production. During the production, transport and storage of proteins, a variety of factors can lead to protein aggregation. With the in-depth study of the phenomenon of protein aggregation, it has been found that there are different pathways and various factors affecting the generation of protein aggregation, such as physicochemical factors, translational modification and protein structure. Since protein aggregation has a significant impact on the activity and homogeneity of proteins, it is very meaningful to understand the pathways of protein aggregation and study how to control aggregation to obtain homogeneous proteins. In this paper, we focus on three protein aggregation pathways, namely 3D structural domain exchange, salt bridge formation, and oxidative stress, as well as methods to control protein aggregation during protein production, transport, and storage, which can help to reduce losses due to protein aggregate formation and to improve the purity and homogeneity of proteins in experimental research and commercial production.

Pathways of Protein Aggregation

• The role of 3D domain swapping in protein aggregation

3D domain swapping is a phenomenon in which two or more partially unfolded monomeric proteins exchange structural domains, and is theoretically universal and reversible for all proteins.3D domain swapping was first proposed in the study of bovine pancreatic ribonuclease (Fig. 1), and has been observed in subsequent studies.

Fig. 2 Structure diagram of bovine pancreatic ribonuclease dimerization via 3D domain swapping

• Role of salt bridges in the formation of aggregates in proteins

A portion of proteins are susceptible to pH effects due to the formation of intrachain salt bridges by amino acid residues leading to the creation of aggregates. The involvement of water molecules and the binding of metal ions have an effect on the salt bridges, and the interchain salt bridges formed by aggregates are more stable than the intrachain salt bridges. The presence of salt bridges promotes the bending of "U" shaped peptides, which further promotes the formation of parallel structures, thus facilitating the formation of protein aggregates in the form of amyloid protofibrils.

Fig. 3 Bovine β-lactoglobulin forms aggregates through salt bridges.

 Methods of Controlling Protein Aggregation

• Modification of protein structure and modification

It has been found that in studies on the influence of protein structure on aggregation, the anti-aggregation ability of proteins can be enhanced by changing the electrostatic potential of the concave surface of the protein-binding region (client-binding surface).

Fig. 4 Changes in the surface charge of rhEPO caused by amino acid site-directed mutagenesis.

Conclusions

In this study, scientist systematically analysed the three main pathways of protein aggregation and the corresponding control strategies, including the regulatory methods targeting hydrophobic interactions, charge interactions and protein structural abnormalities. Effective control strategies are proposed for different pathways, which provide important references for the in-depth understanding of protein aggregation mechanisms and the development of related interventions. This study is expected to provide new ideas and methods to prevent the occurrence of protein aggregation-related diseases.

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