Selenium-containing 15-mer peptides with high glutathione peroxidase-like activity

Glutathione peroxidase (GPX) is one of the most crucial antioxidant enzymes in a variety of organisms. Here we described a new strategy for generating a novel GPX mimic by combination of a phage-displayed random 15-mer peptide library followed by computer-aided rational design and chemical mutation. The novel GPX mimic is a homodimer consisting of a 15-mer selenopeptide with an appropriate catalytic center, a specific binding site for substrates, and high catalytic efficiency. Its steady state kinetics was also studied, and the values of k(cat)/K(m)(GSH) and k(cat)/ K(mH(2)O(2)) were found to be similar to that of native GPX and the highest among the existing GPX mimics. Moreover, the novel GPX mimic was confirmed to have a strong antioxidant ability to inhibit lipid peroxidation by measuring the content of malondialdehyde, cell viability, and lactate dehydrogenase activity. Importantly, the novel GPX mimic can penetrate into the cell membrane because of its small molecular size. These characteristics endue the novel mimic with potential perspective for pharmaceutical applications.     

Repeated horizontal gene transfer of GALactose metabolism genes violates Dollo’s law of irreversible loss

Dollo’s law posits that evolutionary losses are irreversible, thereby narrowing the potential paths of evolutionary change. While phenotypic reversals to ancestral states have been observed, little is known about their underlying genetic causes. The genomes of budding yeasts have been shaped by extensive reductive evolution, such as reduced genome sizes and the losses of metabolic capabilities. However, the extent and mechanisms of trait reacquisition after gene loss in yeasts have not been thoroughly studied. Here, through phylogenomic analyses, we reconstructed the evolutionary history of the yeast galactose utilization pathway and observed widespread and repeated losses of the ability to utilize galactose, which occurred concurrently with the losses of GALactose (GAL) utilization genes. Unexpectedly, we detected multiple galactose-utilizing lineages that were deeply embedded within clades that underwent ancient losses of galactose utilization. We show that at least two, and possibly three, lineages reacquired the GAL pathway via yeast-to-yeast horizontal gene transfer. Our results show how trait reacquisition can occur tens of millions of years after an initial loss via horizontal gene transfer from distant relatives. These findings demonstrate that the losses of complex traits and even whole pathways are not always evolutionary dead-ends, highlighting how reversals to ancestral states can occur.     

Peroxisome-targeted and tandem repeat multimer expressions of human antimicrobial peptide LL37 in Pichia pastoris

Although the human antimicrobial peptide LL37 has a broad spectrum of antimicrobial activities, it easily damages host cells following heterologous expressions. This study attempted two strategies to alleviate its damage to host cells when expressed in Pichia pastoris using the AOX1 promoter. Tandem repeat multimers of LL37 were first designed, and secretion expression strains GS115-9K-(DPLL37DP)_n (n?=?2, 4, 6 and 8) containing different copies of the LL37 gene were constructed. However, LL37 tandems still killed the cells after 96?hr of induction. Subsequently, peroxisome-targeted expression was performed by adding a peroxisomal targeting signal 1 (SKL) at the C-terminus of LL37. The LL37 expression strain GS115-3.5K-LL37-SKL showed no significant inhibition in the cells after induction. Antibacterial activity assays showed that the recombinant LL37 expressed in peroxisomes had good antimicrobial activities. Then, a strain GS115-3.5K-LL37-GFP-SKL producing LL37, green fluorescent protein, and SKL fusion proteins was constructed, and the fusion protein was confirmed to be targeting the peroxisomes. However, protein extraction analysis indicated that most of the fusion proteins were still located in the cell debris after cell disruption, and further studies are required to extract more proteins from the peroxisome membrane.     

Case of a stronger capability of maize seedlings to use ammonium being responsible for the higher 15N recovery efficiency of ammonium compared with nitrate

Plant and Soil - Biocrusts are important functional units in dryland ecosystems. Regarded as ecosystem engineers, cyanobacteria in biocrusts contribute several major physico-chemical and biological...     

MGMT Promoter Methylation Correlates with an Overall Survival Benefit in Chinese High-Grade Glioblastoma Patients Treated with Radiotherapy and Alkylating Agent-Based Chemotherapy: A Single-Institution Study

Promoter methylation of the O⁶-methylguanine-DNA-methyltransferase (MGMT) gene has been considered a prognostic marker and has become more important in the treatment of glioblastoma. However, reports on the correlation between MGMT and clinical outcomes in Chinese glioblastoma patients are very scarce. In this study, quantitative methylation data were obtained by the pyrosequencing of tumor tissues from 128 GBM patients. The median overall survival (OS) was 13.1 months, with a 1-year survival of 45.3%. The pyrosequencing data were reproducible based on archived samples yielding data for all glioblastomas. MGMT promoter methylation was detected in 75/128 cases (58.6%), whereas 53/128 (41.4%) cases were unmethylated. Further survival analysis also revealed that methylation was an independent prognostic factor associated with prolonged OS but not with progression-free survival (PFS) (p = 0.029 and p = 0.112, respectively); the hazard radios were 0.63 (95% CI: 0.42–0.96) and 0.72 (95% CI: 0.48–1.09), respectively. These data indicated that MGMT methylation has prognostic significance in patients with newly diagnosed high-grade glioblastoma undergoing alkylating agent-based chemotherapy after surgical resection.     

Removal of PsaF alters forward electron transfer in photosystem I: evidence for fast reoxidation of QK-A in subunit deletion mutants of Synechococcus sp. PCC 7002

Recent studies of point mutations in photosystem I have suggested that the two kinetic phases of phylloquinone reoxidation represent electron transfer in the two branches of cofactors. This interpretation implies that changes in the relative amplitudes of the two kinetic phases represent a change in the extent of electron transfer in the two branches. Using time-resolved electron paramagnetic resonance (EPR), this issue is investigated in subunit deletion mutants of Synechococcus sp. PCC 7002. The spin-polarized EPR signals of P(700)(+)A(1)(-) and P(700)(+)FeS(-), both at room temperature and in frozen solution, are altered by deletion of PsaF and/or PsaE, and the differences from the wild type are much more pronounced in PS I complexes isolated from the mutants using Triton X-100 rather than n-dodecyl beta-d-maltopyranoside. The changes in the transient EPR data for the mutant complexes are consistent with a significant fraction of reaction centers showing (i) faster electron transfer from A(1)(-) to F(X), (ii) slower forward electron transfer from A(0)(-) to A(1), and (iii) slightly altered quinone hyperfine couplings, possibly as a result of a change in the hydrogen bonding. The fraction of fast electron transfer and its dependence on the isolation procedure are estimated approximately from simulations of the room temperature EPR data. The results are discussed in terms of possible models for the electron transfer. It is suggested that the detergent-induced fraction of fast electron transfer is most likely due to alteration of the environment of the quinone in the PsaA branch of cofactors and is not the result of a change in the directionality of electron transfer.