Strategies for Making Multimeric and Polymeric Bifunctional Protein Conjugates and Their Applications as Bioanalytical Tools

Bifunctional chimeras of myeloperoxidase and glucose oxidase. Antimicrobial, topological and enzymatic properties

Enhancing the local substrate concentration is a crucial strategy in nature for facilitating the proximity of two enzymes. The substrate of the first enzyme is transformed into a by-product that travels to the active site of the second enzyme without external diffusion, then transformed into a product and eventually expelled from the complex. In an effort to optimize the antimicrobial properties of myeloperoxidase from Rhodopirellula baltica (RbMPO), we created a library of fused chimeras between a glucose oxidase (GOx) and RbMPO so that H2O2 could be continuously perfused in the vicinity RbMPO, enabling the production of HOCl or HOSCN, well-known antimicrobial agents. The enzymes were characterized biochemically, enzymatically, and physically using low-resolution techniques such as AFM, SAXS, and cryofracture. SAXS experiments revealed that the chimeras were properly folded and existed in different oligomeric states. The kinetic parameters of the chimeras were determined and used for classification, revealing that all chimeras exhibited varying levels of activity and were microbicidal. The mixture of different oligomeric states of LEGGEAEA displayed both activity and microbicidal properties. AFM was used to visualize the chimeras in different oligomeric states, with their overall shapes ranging from round, oblong, to hooked, depending on the linker used.

Immobilized Horseradish Peroxidase on Enriched Diazo-Activated Silica Gel Harnessed High Biocatalytic Performance at a Steady State in Organic Solvent

Dimethyldichlorosilane (DMDCS), an efficient silane coupling reagent appearing between the -OH groups of silica gel (SG) and picric acid, instantaneously produces a derivative enriched with nitro groups. The nitro group acting as an end-cap terminates the reaction and subsequently was converted into diazo to couple tyrosine's phenol ring via its O-carbon, the inert center to immobilize horseradish peroxidase (HRP) in a multipoint mode. It maintains the status quo of the native enzyme's protein folding and the entire protein groups' chemistry. The molecular formula of the synthesized material was verified and appeared as {Si(OSi)4 (H2O)x}n{-O-Si(CH3)2-O-C6H2(N+≡N)3(HRP)}4·yH2O; the parameters were evaluated as x = 0.5, n = 1158, and y = 752. The immobilized biocatalyst's activity in organic solvents was 1.5 times better than that in an aqueous medium; it worked smoothly, wherein the activity in both solvents stabilized at six months and continued up to nine months at 63 ± 3% compared to the initial.

Designed protein multimerization and polymerization for functionalization of proteins

Abstract

Multimeric and polymeric proteins are large biomacromolecules consisting of multiple protein molecules as their monomeric units, connected through covalent or non-covalent bonds. Genetic modification and post-translational modifications (PTMs) of proteins offer alternative strategies for designing and creating multimeric and polymeric proteins. Multimeric proteins are commonly prepared by genetic modification, whereas polymeric proteins are usually created through PTMs. There are two methods that can be applied to create polymeric proteins: self-assembly and crosslinking. Self-assembly offers a spontaneous reaction without a catalyst, while the crosslinking reaction offers some catalyst options, such as chemicals and enzymes. In addition, enzymes are excellent catalysts because they provide site-specificity, rapid reaction, mild reaction conditions, and activity and functionality maintenance of protein polymers. However, only a few enzymes are applicable for the preparation of protein polymers. Most of the other enzymes are effective only for protein conjugation or labeling. Here, we review novel and applicable strategies for the preparation of multimeric proteins through genetic modification and self-assembly. We then describe the formation of protein polymers through site-selective crosslinking reactions catalyzed by enzymes, crosslinking reactions of non-natural amino acids, and protein-peptide (SpyCatcher/SpyTag) interactions. Finally, we discuss the potential applications of these protein polymers.

Graphical abstract