2-Ketopropyl-coenzyme M oxidoreductase/carboxylase (2-KPCC) is a member of the flavin and cysteine disulfide containing oxidoreductase family (DSOR) that catalyzes the unique reaction between atmospheric CO2 and a ketone/enolate nucleophile to generate acetoacetate. However, the mechanism of this reaction is not well understood. Here, we present evidence that 2-KPCC, in contrast to the well-characterized DSOR enzyme glutathione reductase, undergoes conformational changes during catalysis. Using a suite of biophysical techniques including limited proteolysis, differential scanning fluorimetry, and native mass spectrometry in the presence of substrates and inhibitors, we observed conformational differences between different ligand-bound 2-KPCC species within the catalytic cycle. Analysis of site-specific amino acid variants indicated that 2-KPCC-defining residues, Phe501-His506, within the active site are important for transducing these ligand induced conformational changes. We propose that these conformational changes promote substrate discrimination between H+ and CO2 to favor the metabolically preferred carboxylation product, acetoacetate. 相似文献
Typically, laboratory studies on the physiological effects of temperature are conducted using stable acclimation temperatures. Nonetheless, information extrapolated from these studies may not accurately represent wild populations living in thermally variable environments. The aim of this study was to compare the growth rate, metabolism and swimming performance of wild Atlantic salmon exposed to cycling temperatures, 16–21°C, and stable acclimation temperatures, 16, 18.5, 21°C. Growth rate, metabolic rate, swimming performance and anaerobic metabolites did not change among acclimation groups, suggesting that within Atlantic salmon's thermal optimum range, temperature variation has no effect on these physiological properties. 相似文献
Seed predation may influence community assembly and invasion dynamics when seed predators preferentially select some seed species over others. However, the role of different seed predators and their preferences for seeds in multiple ecological contexts, including the endangered California sage scrub ecosystem, remain unresolved making predictions about which processes limit or promote invasions difficult. In addition, selection criteria, specifically how seed size and biogeographic origin (native versus invasive) influences selection, requires further research across multiple granivore guilds. We examined seed predator preference for common native and invasive seeds across small and large seed classes using seed dish experiments with motion-sensor video observation. We also quantified the relative importance of ants, birds, and mammals as seed predators in sage scrub. Community-wide, granivores preferred the small-seeded invasive mustard Brassica nigra, avoided the large-seeded invasive grass Bromus rubens and the native large-seeded shrub Encelia californica, and did not show significant selection or avoidance for the small-seeded native shrub Salvia apiana. Birds, notably California towhees (Melozone crissalis), were the most frequent granivore while rodents and ants rarely removed seeds. This study reveals that birds are important seed predators in California sage scrub and have the potential to contribute to biotic resistance to mustard invasions (Brassica nigra and potentially others).
Malaria in pregnancy has important consequences for mother and baby. Coverage with the World Health Organization–recommended prevention strategy for pregnant women in sub-Saharan Africa of intermittent preventive treatment in pregnancy (IPTp) and insecticide-treated nets (ITNs) is low. We conducted a systematic review to explore factors affecting delivery, access, and use of IPTp and ITNs among healthcare providers and women.
Methods and Results
We searched the Malaria in Pregnancy Library and Global Health Database from 1 January 1990 to 23 April 2013, without language restriction. Data extraction was performed by two investigators independently, and data was appraised for quality and content. Data on barriers and facilitators, and the effect of interventions, were explored using content analysis and narrative synthesis. We conducted a meta-analysis of determinants of IPTp and ITN uptake using random effects models, and performed subgroup analysis to evaluate consistency across interventions and study populations, countries, and enrolment sites. We did not perform a meta-ethnography of qualitative data.Ninety-eight articles were included, of which 20 were intervention studies. Key barriers to the provision of IPTp and ITNs were unclear policy and guidance on IPTp; general healthcare system issues, such as stockouts and user fees; health facility issues stemming from poor organisation, leading to poor quality of care; poor healthcare provider performance, including confusion over the timing of each IPTp dose; and women''s poor antenatal attendance, affecting IPTp uptake. Key determinants of IPTp coverage were education, knowledge about malaria/IPTp, socio-economic status, parity, and number and timing of antenatal clinic visits. Key determinants of ITN coverage were employment status, education, knowledge about malaria/ITNs, age, and marital status. Predictors showed regional variations.
Conclusions
Delivery of ITNs through antenatal clinics presents fewer problems than delivery of IPTp. Many obstacles to IPTp delivery are relatively simple barriers that could be resolved in the short term. Other barriers are more entrenched within the overall healthcare system or socio-economic/cultural contexts, and will require medium- to long-term strategies.
Please see later in the article for the Editors'' Summary相似文献
RhoH is a hematopoietic-specific, GTPase-deficient member of the Rho GTPase family that was first identified as a hypermutable gene in human B lineage lymphomas. RhoH remains in a constitutively active state and thus its effects are regulated by expression levels or post-translational modifications. Similar to other small GTPases, intracellular localization of RhoH is dependent upon the conserved “CAAX” box and surrounding sequences within the carboxyl (C) terminus. However, RhoH also contains a unique C-terminal “insert” domain of yet undetermined function. RhoH serves as adaptor molecule in T cell receptor signaling and RhoH expression correlates with the unfavorable prognostic marker ZAP70 in human chronic lymphocytic leukemia. Disease progression is attenuated in a Rhoh−/− mouse model of chronic lymphocytic leukemia and treatment of primary human chronic lymphocytic leukemia cells with Lenalidomide results in reduced RhoH protein levels. Thus, RhoH is a potential therapeutic target in B cell malignancies. In the current studies, we demonstrate that deletion of the insert domain (LFSINE) results in significant cytoplasmic protein accumulation. Using inhibitors of degradation pathways, we show that LFSINE regulates lysosomal RhoH uptake and degradation via chaperone-mediated autophagy. Whereas the C-terminal prenylation site is critical for ZAP70 interaction, subcellular localization and rescue of the Rhoh−/− T cell defect in vivo, the insert domain appears dispensable for these functions. Taken together, our findings suggest that the insert domain regulates protein stability and activity without otherwise affecting RhoH function. 相似文献