Phosphorylation of Staphylococcus aureus Protein-Tyrosine Kinase Affects the Function of Glucokinase and Biofilm Formation

Staphylococcus aureus: biofilm formation and strategies against it

The formation of Staphylococcus aureus biofilm causes significant infections in the human body. Biofilm forms through the aggregation of bacterial species and brings about many complications. It mediates drug resistance and persistence and facilitates the recurrence of infection at the end of antimicrobial therapy. Biofilm formation goes through a series of steps to complete, and any interference in these steps can disrupt its formation. Such interference may occur at any stage of biofilm production, including attachment, monolayer formation, and accumulation. Interfering agents can act as quorum sensing inhibitors and interfere in the functionality of quorum sensing receptors, attachment inhibitors and affect the cell hydrophobicity. Among these inhibiting strategies, attachment inhibitors could serve as the best agents against biofilm formation. If pathogens abort the attachment, the following stages of biofilm formation, e.g., accumulation and dispersion, will fail to materialize. Inhibition at this stage leads to suppression of virulence factors and invasion. One of the best-known inhibitors is a chelator that collects metal, Fe+, Zn+, and magnesium critical for biofilm formation. These influential factors in the binding and formation of biofilm are investigated, and the coping strategy is discussed. This review examines the stages of biofilm formation and determines what factors interfere in the continuity of these steps. Finally, the inhibition strategies are investigated, reviewed, and discussed. Keywords: Biofilm, Staphylococcus, Biofilm inhibitor, Dispersion, Antibiofilm agent, EPS, PIA.

Environmental factors modulate biofilm formation by Staphylococcus aureus

Biofilm formation on indwelling medical devices represents an exclusive evasion mechanism for many pathogenic bacteria to establish chronic infections. Staphylococcus aureus is one of the major bacterial pathogens that are able to induce both animal and human infections. The continued emergence of multiple drug-resistant S. aureus, especially methicillin-resistant S. aureus, is problematic due to limited treatment options. Biofilm formation by S. aureus complicates the treatment of methicillin-resistant S. aureus infections. Therefore, elucidating the mechanisms of biofilm formation in this pathogen is important for the development of alternative therapeutic strategies. Various environmental and genetic factors contribute to biofilm formation. In this review, we address the environmental factors and discuss how they affect biofilm formation by S. aureus.

Studying the phosphoryl transfer mechanism of the E. coli phosphofructokinase-2: from X-ray structure to quantum mechanics/molecular mechanics simulations

Phosphofructokinases catalyze the ATP-dependent phosphorylation of fructose-6-phosphate and they are highly regulated.

Phosphofructokinases (Pfks) catalyze the ATP-dependent phosphorylation of fructose-6-phosphate (F6P) and they are regulated in a wide variety of organisms. Although numerous aspects of the kinetics and regulation have been characterized for Pfks, the knowledge about the mechanism of the phosphoryl transfer reaction and the transition state lags behind. In this work, we describe the X-ray crystal structure of the homodimeric Pfk-2 from E. coli, which contains products in one site and reactants in the other, as well as an additional ATP molecule in the inhibitory allosteric site adjacent to the reactants. This complex was previously predicted when studying the kinetic mechanism of ATP inhibition. After removing the allosteric ATP, molecular dynamic (MD) simulations revealed conformational changes related to domain packing, as well as stable interactions of Lys27 and Asp256 with donor (ATP) and acceptor (fructose-6-) groups, and of Asp166 with Mg²⁺. The phosphoryl transfer reaction mechanism catalyzed by Pfk-2 was investigated through Quantum Mechanics/Molecular Mechanics (QM/MM) simulations using a combination of the string method and a path-collective variable for the exploration of its free energy surface. The calculated activation free energies showed that a dissociative mechanism, occurring with a metaphosphate intermediate formation followed by a proton transfer to Asp256, is more favorable than an associative one. The structural analysis reveals the role of Asp256 acting as a catalytic base and Lys27 stabilizing the transition state of the dissociative mechanism.