Site-specific bioconjugation of an organometallic electron mediator to an enzyme with retained photocatalytic cofactor regenerating capacity and enzymatic activity

Metagenomic exploration of multi-resistance genes linked to microbial attributes in active nonferrous metal(loid) tailings

Mine tailings sites are considered as a continuous source of discharged metal(loid)s and residual organic flotation reagents. They are extremely toxic environments representing unique ecological niches for microbial communities. Mine tailings as a source of multi-resistance genes have been poorly investigated. Metagenomic analysis for four active nonferrous metal(loid) tailings sites with different environmental parameters was conducted. The abundance of Thiobacillus, able to tolerate acidity and showing iron- and sulfur/sulfide oxidation capacities, was significantly different (p < 0.05) between acid and neutral tailings sites. Correlation analyses showed that Zn, Pb, TP, Cd, and Cu were the main drivers influencing the bacterial compositions. Multi-metal resistance genes (MRGs) and antibiotic resistance genes (ARGs), such as baca and copA, were found to be co-selected by high concentrations of metal(loid)s tailings. The main contributors to different distributions of MRGs were Thiobacillus and Nocardioides genus, while genera with low abundance (<0.1%) were the main contributors for ARGs. Functional metabolic pathways related to Fe-S metabolism, polycyclic aromatic hydrocarbons (PAHs) degradation and acid stress were largely from Altererythrobacter, Lysobacter, and Thiobacillus, respectively. Such information provides new insights on active tailings with highly toxic contaminants. Short-term metal(loid) exposure of microorganism in active nonferrous metal(loid) tailings contribute to the co-occurrence of ARGs and MRGs, and aggravation of tailings acidification. Our results recommend that the management of microorganisms involved in acid tolerance and metal/antibiotic resistance is of key importance for in-suit treatment of the continuous discharge of tailings with multiple metal(loid) contaminants into impoundments.

Generation of therapeutic protein variants with the human serum albumin binding capacity via site-specific fatty acid conjugation

Extension of the serum half-life is an important issue in developing new therapeutic proteins and expanding applications of existing therapeutic proteins. Conjugation of fatty acid, a natural human serum albumin ligand, to a therapeutic protein/peptide was developed as a technique to extend the serum half-life in vivo by taking advantages of unusually long serum half-life of human serum albumin (HSA). However, for broad applications of fatty acid-conjugation, several issues should be addressed, including a poor solubility of fatty acid and a substantial loss in the therapeutic activity. Therefore, herein we systematically investigate the conditions and components in conjugation of fatty acid to a therapeutic protein resulting in the HSA binding capacity without compromising therapeutic activities. By examining the crystal structure and performing dye conjugation assay, two sites (W160 and D112) of urate oxidase (Uox), a model therapeutic protein, were selected as sites for fatty acid-conjugation. Combination of site-specific incorporation of a clickable p-azido-L-phenylalanine to Uox and strain-promoted azide-alkyne cycloaddition allowed the conjugation of fatty acid (palmitic acid analog) to Uox with the HSA binding capacity and retained enzyme activity. Deoxycholic acid, a strong detergent, greatly enhanced the conjugation yield likely due to the enhanced solubility of palmitic acid analog.

Controlled Orientation of Active Sites in a Nanostructured Multienzyme Complex

Multistep cascade reactions in nature maximize reaction efficiency by co-assembling related enzymes. Such organization facilitates the processing of intermediates by downstream enzymes. Previously, the studies on multienzyme nanocomplexes assembled on DNA scaffolds demonstrated that closer interenzyme distance enhances the overall reaction efficiency. However, it remains unknown how the active site orientation controlled at nanoscale can have an effect on multienzyme reaction. Here, we show that controlled alignment of active sites promotes the multienzyme reaction efficiency. By genetic incorporation of a non-natural amino acid and two compatible bioorthogonal chemistries, we conjugated mannitol dehydrogenase to formate dehydrogenase with the defined active site arrangement with the residue-level accuracy. The study revealed that the multienzyme complex with the active sites directed towards each other exhibits four-fold higher relative efficiency enhancement in the cascade reaction and produces 60% more D-mannitol than the other complex with active sites directed away from each other.

Double clicking for site-specific coupling of multiple enzymes

Herein, we report a novel strategy to site-specifically couple multiple enzymes using two compatible click chemistries and site-specific incorporation of a clickable non-natural amino acid.