Bacillus anthracis Prolyl 4-Hydroxylase Interacts with and Modifies Elongation Factor Tu

Diffusion model assisted designing self-assembling collagen mimetic peptides as biocompatible materials

Collagen self-assembly supports its mechanical function, but controlling collagen mimetic peptides (CMPs) to self-assemble into higher-order oligomers with numerous functions remains challenging due to the vast potential amino acid sequence space. Herein, we developed a diffusion model to learn features from different types of human collagens and generate CMPs; obtaining 66% of synthetic CMPs could self-assemble into triple helices. Triple-helical and untwisting states were probed by melting temperature (Tm); hence, we developed a model to predict collagen Tm, achieving a state-of-art Pearson's correlation (PC) of 0.95 by cross-validation and a PC of 0.8 for predicting Tm values of synthetic CMPs. Our chemically synthesized short CMPs and recombinantly expressed long CMPs could self-assemble, with the lowest requirement for hydrogel formation at a concentration of 0.08% (w/v). Five CMPs could promote osteoblast differentiation. Our results demonstrated the potential for using computer-aided methods to design functional self-assembling CMPs.

P4HA2 knockdown prevents the progression of intracranial aneurysm by inducing prolyl hydroxylation of YAP1

Prolyl 4-hydroxylase subunit alpha 2 (P4HA2), a key enzyme modulating the post-transcription of proteins, was reported to be a causative gene in IA. Nevertheless, the exact function and mechanism of P4HA2 in the formation and rupture of IA is elusive. The current study first explored the expression of P4HA2 and its association with the clinicopathological demonstrations in patients with IA. In addition, an in vitro model of IA was established using H2O2 to stimulate vascular smooth muscle cells (VSMCs). The behaviors of treated VSMCs were evaluated using CCK-8, Wound healing, and Transwell assays. The expression of genes was detected by RT-qPCR and Western blot. Interaction between genes was confirmed using Luciferase Reporter assay and Co-immunoprecipitation (Co-IP) assay. Our results revealed that P4HA2 expression was upregulated in IA, especially ruptured IA; high P4HA2 expression correlates with unfavorable clinicopathological parameters. Through the in vitro experiments, it was discovered that P4HA2 knockdown rescued VSMCs from H2O2-induced viability impairment, enhancement in migration and apoptosis, switch from contractile phenotype, and augmentation of oxidative stress and inflammation. Mechanistically, P4HA2 was found to trigger the prolyl hydroxylation of YAP1 to negatively regulate the transcriptional activity of YAP1 in H2O2-challenged VSMCs. The effect of P4HA2 on H2O2-challenged VSMCs could be annulled by the mutation of YAP1 hydroxylation sites. In summary, P4HA2 served as a contributing factor during IA progression through its suppression on YAP1 activity by prolyl hydroxylation.

Machine learning-assisted substrate binding pocket engineering based on structural information

Engineering enzyme-substrate binding pockets is the most efficient approach for modifying catalytic activity, but is limited if the substrate binding sites are indistinct. Here, we developed a 3D convolutional neural network for predicting protein-ligand binding sites. The network was integrated by DenseNet, UNet, and self-attention for extracting features and recovering sample size. We attempted to enlarge the dataset by data augmentation, and the model achieved success rates of 48.4%, 35.5%, and 43.6% at a precision of ≥50% and 52%, 47.6%, and 58.1%. The distance of predicted and real center is ≤4 Å, which is based on SC6K, COACH420, and BU48 validation datasets. The substrate binding sites of Klebsiella variicola acid phosphatase (KvAP) and Bacillus anthracis proline 4-hydroxylase (BaP4H) were predicted using DUnet, showing high competitive performance of 53.8% and 56% of the predicted binding sites that critically affected the catalysis of KvAP and BaP4H. Virtual saturation mutagenesis was applied based on the predicted binding sites of KvAP, and the top-ranked 10 single mutations contributed to stronger enzyme-substrate binding varied while the predicted sites were different. The advantage of DUnet for predicting key residues responsible for enzyme activity further promoted the success rate of virtual mutagenesis. This study highlighted the significance of correctly predicting key binding sites for enzyme engineering.

Biochemistry of the hypoxia-inducible factor hydroxylases

The hypoxia-inducible factors are α,β-heterodimeric transcription factors that mediate the chronic response to hypoxia in humans and other animals. Protein hydroxylases belonging to two different structural subfamilies of the Fe(II) and 2-oxoglutarate (2OG)-dependent oxygenase superfamily modify HIFα. HIFα prolyl-hydroxylation, as catalysed by the PHDs, regulates HIFα levels and, consequently, α,β-HIF levels. HIFα asparaginyl-hydroxylation, as catalysed by factor inhibiting HIF (FIH), regulates the transcriptional activity of α,β-HIF. The activities of the PHDs and FIH are regulated by O2 availability, enabling them to act as hypoxia sensors. We provide an overview of the biochemistry of the HIF hydroxylases, discussing evidence that their kinetic and structural properties may be tuned to their roles in the HIF system. Avenues for future research and therapeutic modulation are discussed.

Anaerobiosis: A Surfactant Helps Bacteria Breathe a Sigh of Relief

Oxygen is essential for many organisms who have therefore evolved mechanisms to enable survival during hypoxia. A new study describes how a well-known bacterial surfactant, called surfactin, facilitates bacterial viability when oxygen becomes limiting by reducing oxygen consumption.

The putative bacterial oxygen sensor Pseudomonas prolyl hydroxylase (PPHD) suppresses antibiotic resistance and pathogenicity in Pseudomonas aeruginosa

Pseudomonas aeruginosa is an extracellular opportunistic bacterial pathogen commonly associated with infectious complications in susceptible individuals, such as those with underlying diseases including HIV/AIDS and cystic fibrosis. Antibiotic resistance in multiple strains of P. aeruginosa is a rapidly developing clinical problem. We have previously demonstrated that the oxygen levels at the site of P. aeruginosa infection can strongly influence virulence and antibiotic resistance in this pathogen, although the oxygen-sensing and -signaling mechanisms underpinning this response have remained unknown. In this study, we investigated the potential role of the putative oxygen sensor Pseudomonas prolyl hydroxylase (PPHD) in the control of virulence and antibiotic resistance in P. aeruginosa We found that a P. aeruginosa strain lacking PPHD (PAO310) exhibits increased virulence associated with increased bacterial motility. Furthermore, PPHD-deficient P. aeruginosa displayed enhanced antibiotic resistance against tetracycline through increased expression of the xenobiotic transporters mexEF-oprN and MexXY. Of note, the effect of the PPHD knockout on antibiotic resistance was phenocopied in bacteria exposed to atmospheric hypoxia. We conclude that PPHD is a putative bacterial oxygen sensor that may link microenvironmental oxygen levels to virulence and antibiotic resistance in P. aeruginosa.

A Toxoplasma Prolyl Hydroxylase Mediates Oxygen Stress Responses by Regulating Translation Elongation

As the protozoan parasite Toxoplasma gondii disseminates through its host, it responds to environmental changes by altering its gene expression, metabolism, and other processes. Oxygen is one variable environmental factor, and properly adapting to changes in oxygen levels is critical to prevent the accumulation of reactive oxygen species and other cytotoxic factors. Thus, oxygen-sensing proteins are important, and among these, 2-oxoglutarate-dependent prolyl hydroxylases are highly conserved throughout evolution. Toxoplasma expresses two such enzymes, TgPHYa, which regulates the SCF-ubiquitin ligase complex, and TgPHYb. To characterize TgPHYb, we created a Toxoplasma strain that conditionally expresses TgPHYb and report that TgPHYb is required for optimal parasite growth under normal growth conditions. However, exposing TgPHYb-depleted parasites to extracellular stress leads to severe decreases in parasite invasion, which is likely due to decreased abundance of parasite adhesins. Adhesin protein abundance is reduced in TgPHYb-depleted parasites as a result of inactivation of the protein synthesis elongation factor eEF2 that is accompanied by decreased rates of translational elongation. In contrast to most other oxygen-sensing proteins that mediate cellular responses to low O2, TgPHYb is specifically required for parasite growth and protein synthesis at high, but not low, O2 tensions as well as resistance to reactive oxygen species. In vivo, reduced TgPHYb expression leads to lower parasite burdens in oxygen-rich tissues. Taken together, these data identify TgPHYb as a sensor of high O2 levels, in contrast to TgPHYa, which supports the parasite at low O2IMPORTANCE Because oxygen plays a key role in the growth of many organisms, cells must know how much oxygen is available. O2-sensing proteins are therefore critical cellular factors, and prolyl hydroxylases are the best-studied type of O2-sensing proteins. In general, prolyl hydroxylases trigger cellular responses to decreased oxygen availability. But, how does a cell react to high levels of oxygen? Using the protozoan parasite Toxoplasma gondii, we discovered a prolyl hydroxylase that allows the parasite to grow at elevated oxygen levels and does so by regulating protein synthesis. Loss of this enzyme also reduces parasite burden in oxygen-rich tissues, indicating that sensing both high and low levels of oxygen impacts the growth and physiology of Toxoplasma.

Differential expression of proteins in the leaves and roots of cadmium-stressed Microsorum pteropus, a novel potential aquatic cadmium hyperaccumulator

Microsorum pteropus is a fully or partially submerged Polypodiaceae fern that has been proven to be a potential Cd aquatic hyperaccumulator. Proteomic analysis was used in this study to investigate the resistance mechanisms of M. pteropus root and leaf tissues under Cd stress. M. pteropus plants were exposed to up to 500 μM Cd in hydroponics for 7 days. The plant can accumulate >4,000 mg/kg Cd in both root and leaf dry mass. Meanwhile, the proteins in roots and leaves in the 500 μM Cd treatment were separated and analyzed by proteomics. Eight proteins with altered expression in roots and twenty proteins with altered expression in leaves were identified using MALDI-TOF/TOF-MS (matrix-assisted laser desorption/ionization time of flight mass spectrometry) in this study. The proteins were involved in energy metabolism, antioxidant activity, cellular metabolism and protein metabolism. However, just three proteins were significantly differentially expressed in both tissues, and they were all involved in basal metabolism, indicating different resistance mechanisms between roots and leaves. Root tissues of M. pteropus mainly resist Cd damage by antioxidants and the enhancement of energy metabolism, while leaf tissues of M. pteropus mainly protect themselves by maintaining photosynthetic functions and the regulation of cellular metabolism.