Artemisinin-resistant Plasmodium falciparum Kelch13 mutant proteins display reduced heme-binding affinity and decreased artemisinin activation.

The potency of frontline antimalarial drug artemisinin (ART) derivatives is triggered by heme-induced cleavage of the endoperoxide bond to form reactive heme-ART alkoxy radicals and covalent heme-ART adducts, which are highly toxic to the parasite. ART-resistant (ART-R) parasites with mutations in the Plasmodium falciparum Kelch-containing protein Kelch13 (PfKekch13) exhibit impaired hemoglobin uptake, reduced yield of hemoglobin-derived heme, and thus decreased ART activation. However, any direct involvement of PfKelch13 in heme-mediated ART activation has not been reported.

Deeper Insights into Mixed Crowding through Enzyme Activity, Dynamics, and Crowder Diffusion.

Given the fact that the cellular interior is crowded by many different kinds of macromolecules, it is important that studies be carried out in the presence of mixed crowder systems. In this regard, we have used binary crowders formed by the combination of some of the commonly used crowding agents, namely, Ficoll 70, Dextran 70, Dextran 40, and PEG 8000 (PEG 8), to study how these affect enzyme activity, dynamics, and crowder diffusion. The enzyme chosen is AK3L1, an isoform of adenylate kinase.

Bridging Soft Interaction and Excluded Volume in Crowded Milieu through Subtle Protein Dynamics.

The impact of macromolecular crowding on biological macromolecules has been elucidated through the excluded volume phenomenon and soft interactions. However, it has often been difficult to provide a clear demarcation between the two regions. Here, using temperature-dependent dynamics (local and global) of the multidomain protein human serum albumin (HSA) in the presence of commonly used synthetic crowders (Dextran 40, PEG 8, Ficoll 70, and Dextran 70), we have shown the presence of a transition that serves as a bridge between the soft and hard regimes.

Towards the energy landscape of adenylate kinase in crowded milieu: Activity, conformation, structure and dynamics in sequence.

Enzyme function is governed by a complex network of conformational changes and internal dynamics, with the same getting more convoluted in the crowded cellular environment. Here, we have explored an intricate interplay amongst activity, structure, conformation, and dynamics of a multidomain enzyme, AK3L1 (UniProtKB: Q9UIJ7) in the crowded milieu. We have monitored changes in the enzyme landscape in response to the chemical denaturant, urea, under the influence of different concentrations of macromolecular crowders.

Enhancement in chaperone activity of human αA-crystallin by nanochaperone gold nanoparticles: Multispectroscopic studies on their molecular interactions.

The chaperone activity of human αA-crystallin (HAA) against aggregation of human γD-crystallin (HGD) was enhanced by gold nanoparticles (AuNPs). Chaperone activity of HAA was almost doubled in the presence of 5.5 nM gold nanoparticles (AuNPs).

Correlating the Local and Global Dynamics of an Enzyme in the Crowded Milieu.

Enzymes are dynamic biological macromolecules, with their catalytic function(s) being largely influenced by the changes in local fluctuations of amino acid side chains as well as global structural modulations that the enzyme undergoes. Such local and global motions can be highly affected inside the crowded physiological interior of the cell. Here, we have addressed the role of dynamic structural flexibility in affecting the activation energy barrier of a flexible multidomain enzyme adenylate kinase (AK3L1, UniProtKB: Q9UIJ7).

Understanding enzyme behavior in a crowded scenario through modulation in activity, conformation and dynamics.

Macromolecular crowding, inside the physiological interior, modulates the energy landscape of biological macromolecules in multiple ways. Amongst these, enzymes occupy a special place and hence understanding the function of the same in the crowded interior is of utmost importance. In this study, we have investigated the manner in which the multidomain enzyme, AK3L1 (PDB ID: 1ZD8), an isoform of adenylate kinase, has its features affected in presence of commonly used crowders (PEG 8, Dextran 40, Dextran 70, and Ficoll 70).

Influence of crowding agents on the dynamics of a multidomain protein in its denatured state: a solvation approach.

It is now well appreciated that the crowded intracellular environment significantly modulates an array of physiological processes including protein folding-unfolding, aggregation, and dynamics to name a few. In this work we have studied the dynamics of domain I of the protein human serum albumin (HSA) in its urea-induced denatured states, in the presence of a series of commonly used macromolecular crowding agents. HSA was labeled at Cys-34 (a free cysteine) in domain I with the fluorophore 6-bromoacetyl-2-dimethylaminonaphthalene (BADAN) to act as a solvation probe.