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To identify genes necessary for the photoproduction of H 2 in Chlamydomonas reinhardtii, random insertional mutants were screened for clones unable to produce H 2 . One of the identified mutants, denoted hydEF-1, is incapable of assembling an active [Fe] hydrogenase. Although the hydEF-1 mutant transcribes both hydrogenase genes and accumulates full-length hydrogenase protein, H 2 production activity is not observed. The HydEF protein contains two unique domains that are homologous to two distinct prokaryotic proteins, HydE and HydF, which are found exclusively in organisms containing [Fe] hydrogenase. In the C. reinhardtii genome, the HydEF gene is adjacent to another hydrogenase-related gene, HydG. Hydrogen has enormous potential to serve as a non-polluting fuel, alleviating the environmental and political concerns associated with fossil energy utilization. Among the most efficient H 2 -generating catalysts known are the [Fe] hydrogenase enzymes, which are found in numerous microorganisms, including the photosynthetic green alga Chlamydomonas reinhardtii (1, 2). Our research, aimed at identifying accessory proteins required for H 2 production in C. reinhardtii, has resulted in the discovery of two [Fe] hydrogenase assembly genes. These genes are essential for the formation of an active [Fe] hydrogenase and are conserved among sequenced organisms containing [Fe] hydrogenase enzymes.Algal H 2 production was first reported by Hans Gaffron and co-workers in seminal experiments performed over 60 years ago (3). Photosynthetic green algae are unique in that H 2 production by [Fe] hydrogenases is coupled directly to water oxidation through photosystem II and the photosynthetic electron transport chain, providing the means to generate H 2 using sunlight. In the past 5 years, great strides have been made in sustaining H 2 photoproduction activity in C. reinhardtii (4, 5), and intensive research continues to probe novel ways to use this and other photosynthetic organisms to generate renewable H 2 .Hydrogenases containing metallo-catalytic clusters occur as [NiFe] or [Fe]-only enzymes (2, 6, 7). These two forms are phylogenetically distinct (8), which suggests that hydrogenase function is the result of convergent evolution (2). Although [NiFe] and [Fe] hydrogenases are genetically unrelated, similarities between the proteins do exist. First, the active sites of both enzymes contain CO and CN ligands, and, second, each active site contains a binuclear metal center. In general, [NiFe] hydrogenases catalyze H 2 uptake, whereas [Fe] hydrogenases tend to catalyze H 2 evolution (9). Furthermore, the turnover number of [Fe] hydrogenases is 10 -100 times higher than that of [NiFe] hydrogenases (9), making the former one of the most efficient H 2 production catalysts known. Hydrogenases containing NiFeSe (10) and a unique class of hydrogenases containing a single Fe atom bound to a co-factor have also been reported (11).The [NiFe] hydrogenases are found in a variety of anaerobic and facultative archaea, eubacteria, a...

AbstractThe outbreak of coronavirus disease (COVID-19) in China caused by SARS-CoV-2 virus continually lead to worldwide human infections and deaths. It is currently no specific viral protein targeted therapeutics yet. Viral nucleocapsid protein is a potential antiviral drug target, serving multiple critical functions during the viral life cycle. However, the structural information of SARS-CoV-2 nucleocapsid protein is yet to be clear. Herein, we have determined the 2.7 Å crystal structure of the N-terminal RNA binding domain of SARS-CoV-2 nucleocapsid protein. Although overall structure is similar with other reported coronavirus nucleocapsid protein N-terminal domain, the surface electrostatic potential characteristics between them are distinct. Further comparison with mild virus type HCoV-OC43 equivalent domain demonstrates a unique potential RNA binding pocket alongside the β-sheet core. Complemented by in vitro binding studies, our data provide several atomic resolution features of SARS-CoV-2 nucleocapsid protein N-terminal domain, guiding the design of novel antiviral agents specific targeting to SARS-CoV-2.

Background Malignant transformation and progression of cancer are driven by the co-evolution of cancer cells and their dysregulated tumor microenvironment (TME). Recent studies on immunotherapy demonstrate the efficacy in reverting the anti-tumoral function of T cells, highlighting the therapeutic potential in targeting certain cell types in TME. However, the functions of other immune cell types remain largely unexplored. Results We conduct a single-cell RNA-seq analysis of cells isolated from tumor tissue samples of non-small cell lung cancer (NSCLC) patients, and identify subtypes of tumor-infiltrated B cells and their diverse functions in the progression of NSCLC. Flow cytometry and immunohistochemistry experiments on two independent cohorts confirm the co-existence of the two major subtypes of B cells, namely the naïve-like and plasma-like B cells. The naïve-like B cells are decreased in advanced NSCLC, and their lower level is associated with poor prognosis. Co-culture of isolated naïve-like B cells from NSCLC patients with two lung cancer cell lines demonstrate that the naïve-like B cells suppress the growth of lung cancer cells by secreting four factors negatively regulating the cell growth. We also demonstrate that the plasma-like B cells inhibit cancer cell growth in the early stage of NSCLC, but promote cell growth in the advanced stage of NSCLC. The roles of the plasma-like B cell produced immunoglobulins, and their interacting proteins in the progression of NSCLC are further validated by proteomics data. Conclusion Our analysis reveals versatile functions of tumor-infiltrating B cells and their potential clinical implications in NSCLC.

Lomaiviticin A and difluostatin A are benzofluorene-containing aromatic polyketides in the atypical angucycline family. Although these dimeric compounds are potent antitumor agents, how nature constructs their complex structures remains poorly understood. Herein, we report the discovery of a number of fluostatin type dimeric aromatic polyketides with varied C−C and C−N coupling patterns. We also demonstrate that these dimers are not true secondary metabolites, but are instead derived from non-enzymatic deacylation of biosynthetic acyl fluostatins. The non-enzymatic deacylation proceeds via a transient quinone methide like intermediate which facilitates the subsequent C–C/C−N coupled dimerization. Characterization of this unusual property of acyl fluostatins explains how dimerization takes place, and suggests a strategy for the assembly of C–C and C–N coupled aromatic polyketide dimers. Additionally, a deacylase FlsH was identified which may help to prevent accumulation of toxic quinone methides by catalyzing hydrolysis of the acyl group.

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Although candidemia has been reported globally, little is known about the differences in candidemia episodes between ICU and surgical wards or the correlation between serum biomarkers and mortality from candidemia. A retrospective study of hospitalized patients with candidemia was conducted in southwest China. A total of 198 non-duplicate candidemia episodes were identified between January 2011 and December 2016. Candida albicans was the leading species causing candidemia (34.9%), and 78.8% of these isolates were susceptible to fluconazole. More than half of candidemic patients were hospitalized in surgical wards, but the incidence of these surgical patients was much lower than that of ICU patients. Compared with surgical patients, patients admitted to ICU were more frequently subjected to extensive invasive procedures, severe clinical presentations, and heavy exposure to antibiotics. In addition, the mortality in ICU was significantly higher than that in surgical wards. Multivariable analysis revealed that ascites, catheter-related candidemia, ICU admission, septic shock, and concomitant bacterial infection were independent factors associated with mortality. Moreover, we observed that high PCT and BDG levels as well as low PLT counts were also associated with mortality from candidemia. Better understanding of the specific predictors in different wards could facilitate the identification of high-risk candidates to receive early antifungal therapy, thus improving the outcomes of critically ill patients with candidemia.

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