Search Results (4)

In the Gram-negative bacteria, many important virulence factors reach their destination via two-step export systems, and they must traverse the periplasmic space before reaching the outer membrane. Since these proteins must be maintained in a structure competent for transport into or across the membrane, they frequently require the assistance of chaperones. Based on the results obtained for the model bacterium Escherichia coli and related species, it is assumed that in the biogenesis of the outer membrane proteins and the periplasmic transit of secretory proteins, the SurA peptidyl–prolyl isomerase/chaperone plays a leading role, while the Skp chaperone is rather of secondary importance. However, detailed studies carried out on several other Gram-negative pathogens indicate that the importance of individual chaperones in the folding and transport processes depends on the properties of client proteins and is species-specific. Taking into account the importance of SurA functions in bacterial virulence and severity of phenotypes due to surA mutations, this folding factor is considered as a putative therapeutic target to combat microbial infections. In this review, we present recent findings regarding SurA and Skp proteins: their mechanisms of action, involvement in processes related to virulence, and perspectives to use them as therapeutic targets. Full article

Activation of pro-σ^K processing requires a signaling protease SpoIVB that is secreted from the forespore into the space between the two cells during sporulation in Bacillus subtilis. Bypass of forespore protein C (BofC) is an inhibitor preventing the autoproteolysis of SpoIVB, ensuring the factor σ^K operates regularly at the correct time during the sporulation. However, the regulatory mechanisms of BofC on pro-σ^K processing are still unclear, especially in the aspect of the interaction between BofC and SpoIVB. Herein, the recombinant BofC (rBofC) was expressed in the periplasm by the E. coli expression system, and crystal growth conditions were obtained and optimized. Further, the crystal structure of rBofC was determined by X-ray crystallography, which is nearly identical to the structures determined by NMR and predicted by AlphaFold. In addition, the modeled structure of the BofC–SpoIVB complex provides insights into the molecular mechanism by which domain 1 of BofC occupies the active site of the SpoIVB serine protease domain, leading to the inhibition of the catalytical activity of SpoIVB and prevention of the substrate of SpoIVB (SpoIVFA) from binding to the active site. Full article

Nitrous oxide is a long-lived greenhouse gas that exists for 114 years in the atmosphere and is 298-fold more potent than carbon dioxide in its global warming potential. Two recent studies showcased the utility of Azolla plants for a lesser footprint in nitrous oxide production from urea and other supplements to the irrigated ecosystem, which mandates exploration since there is still no clear solution to nitrous oxide in paddy fields or in other ecosystems. Here, we propose a solution based on the evolution of a single cytochrome oxidase subunit II protein (WP_013192178.1) from the cyanobiont Trichormus azollae that we hypothesize to be able to quench nitrous oxide. First, we draw attention to a domain in the candidate protein that is emerging as a sensory periplasmic Y_Y_Y domain that is inferred to bind nitrous oxide. Secondly, we draw the phylogeny of the candidate protein showcasing the poor bootstrap support of its position in the wider clade showcasing its deviation from the core function. Thirdly, we show that the NtcA protein, the apical N-effecting transcription factor, can putatively bind to a promoter sequence of the gene coding for the candidate protein (WP_013192178.1), suggesting a function associated with heterocysts and N-metabolism. Our fourth point involves a string of histidines at the C-terminal extremity of the WP_013192178.1 protein that is missing on all other T. azollae cytochrome oxidase subunit II counterparts, suggesting that such histidines are perhaps involved in forming a Cu center. As the fifth point, we showcase a unique glycine-183 in a lengthy linker region containing multiple glycines that is absent in all proximal Nostocales cyanobacteria, which we predict to be a DNA binding residue. We propose a mechanism of action for the WP_013192178.1 protein based on our in silico analyses. In total, we hypothesize the incomplete and rapid conversion of a likely heterocystous cytochrome oxidase subunit II protein to an emerging nitrous oxide sensing/quenching subunit based on bioinformatics analyses and past literature, which can have repercussions to climate change and consequently, future human life. Full article

The epidermal growth factor receptor (EGFR) was found to be a valuable target on prostate cancer (PCa) cells. However, EGFR inhibitors mostly failed in clinical studies with patients suffering from PCa. We therefore tested the targeted toxins EGF-PE40 and EGF-PE24mut consisting of the natural ligand EGF as binding domain and PE40, the natural toxin domain of Pseudomonas Exotoxin A, or PE24mut, the de-immunized variant thereof, as toxin domains. Both targeted toxins were expressed in the periplasm of E.coli and evoked an inhibition of protein biosynthesis in EGFR-expressing PCa cells. Concentration- and time-dependent killing of PCa cells was found with IC₅₀ values after 48 and 72 h in the low nanomolar or picomolar range based on the induction of apoptosis. EGF-PE24mut was found to be about 11- to 120-fold less toxic than EGF-PE40. Both targeted toxins were more than 600 to 140,000-fold more cytotoxic than the EGFR inhibitor erlotinib. Due to their high and specific cytotoxicity, the EGF-based targeted toxins EGF-PE40 and EGF-PE24mut represent promising candidates for the future treatment of PCa. Full article