Interaction between bacterial outer membrane proteins and periplasmic quality control factors: a kinetic partitioning mechanism

The OMPs (outer membrane proteins) of Gram-negative bacteria have to be translocated through the periplasmic space before reaching their final destination. The aqueous environment of the periplasmic space and high permeability of the outer membrane engender such a translocation process inevitably challenging. In Escherichia coli, although SurA, Skp and DegP have been identified to function in translocating OMPs across the periplasm, their precise roles and their relationship remain to be elucidated. In the present paper, by using fluorescence resonance energy transfer and single-molecule detection, we have studied the interaction between the OMP OmpC and these periplasmic quality control factors. The results of the present study reveal that the binding rate of OmpC to SurA or Skp is much faster than that to DegP, which may lead to sequential interaction between OMPs and different quality control factors. Such a kinetic partitioning mechanism for the chaperone-substrate interaction may be essential for the quality control of the biogenesis of OMPs.     

Variation in structural and physiological leaf traits of eight species in karst desertification area of China

Leaf traits have long been recognized as influential factors in the acquisition and processing of resources by plants. However, there is less knowledge of between-species variations in seasonal changes in leaf traits and trait interrelationships. Therefore, we examined variations in leaf area (LA), dry biomass (DM), specific leaf area (SLA), and leaf gas-exchange parameters in one non-native and seven native tree species under field environmental conditions, in a karst area in China subjected to desertification. Measurements were taken three times during the growing season. The results show that the seven native trees had higher LA, DM, and water-use efficiency (WUE) than the non-native Cinnamomum camphora. In contrast, all the native tree species except Ligustrum lucidum had lower photosynthetic rates (P _N) than the non-native species. In all species, the relationship between LA and DM was less variable than the relationship between SLA and LA. However, leaves of the non-native C. camphora and native species Sterculia lanceolata, Cleidiocarpon cavalerei and Cyclobalanopsis glauca were highly sensitive to seasonal conditions, leaves of Sapindus mukorossi and Ligustrum lucidum were less sensitive to seasonal changes, and leaves of Syzygium cumini and Cephalomappa sinensis were insensitive. An understanding of leaf traits will aid the selection of suitable species for land restoration.     

Cloning and expression of stearoyl-CoA desaturase 1 (SCD-1) in the liver of the Sichuan white goose and landes goose responding to overfeeding

The EST sequence of goose (Anser cygnoides) Stearoyl-CoA desaturase 1(SCD-1) was obtained from a subtractive cDNA library. To further investigate the role of SCD-1 in lipid metabolism in geese, 5′-RACE and 3′-RACE were carried out in this study to obtain the complete cDNA sequence of goose SCD-1, which contained a 29-bp 5′ UTR, a 1074-bp open reading frame (ORF) encoding 357 amino acids, and a 125-bp 3′ UTR. The expression of SCD-1 was measured in several tissues, and the effects of overfeeding on the expression of SCD-1 were studied. The results of real time RT-PCR demonstrated that, compared to the brain, goose SCD-1 mRNA was more abundant in the liver. Overfeeding markedly increased the mRNA expression of SCD-1 in the liver of Sichuan White and Landes geese, and gene expression was markedly higher in the Sichuan White goose than in the landes goose. The mRNA abundance of SCD-1 in the liver had significant positive correlations with triacylglycerol (TG) content in liver lipids and in the levels of plasma insulin and very low-density lipoproteins (VLDL) levels in Sichuan white geese. However, the mRNA abundance of SCD-1 in the livers of Landes geese had only significant positive correlations with the TG content in liver lipids. In conclusion, SCD-1 is not only critical for hepatic steatosis in geese but is also important for the difference in lipid deposition in the livers of the two breeds.     

Bioengineering of the Enterobacter aerogenes strain for biohydrogen production

Enterobacter aerogenes is one of the most widely-studied model strains for fermentative hydrogen production. To improve the hydrogen yield of E. aerogenes, the bioengineering on a biomolecular level and metabolic network level is of importance. In this review, the fermentative technology of E. aerogenes for hydrogen production will be first briefly summarized. And then the bioengineering of E. aerogenes for the improvement of hydrogen yield will be thoroughly reviewed, including the anaerobic metabolic networks for hydrogen evolution in E. aerogenes, metabolic engineering for improving hydrogen production in E. aerogenes and mixed culture of E. aerogenes with other hydrogen-producing bacteria to enhance the overall yield in anaerobic cultivation. Finally, a perspective on E. aerogenes as a hydrogen producer including systems bioengineering approach for improving the hydrogen yield and application of the engineered E. aerogenes in mixed culture will be presented.     

Synthesis and acrosin inhibitory activities of substituted ethyl 5-(4-aminophenyl)-1H-pyrazole-3-carboxylate derivatives

A series of novel ethyl 5-(4-aminophenyl)-1H-pyrazole-3-carboxylate derivatives were designed and synthesized and their in vitro acrosin inhibitory activities were evaluated. Most of the compounds exhibited acrosin inhibitory activities. Among them, three compounds (5l, 5n, and 5v) were more potent than that of the control TLCK. These provide a new structural type for the development of novel contraceptive acrosin inhibitory agents.     

Genome sequence of Corynebacterium glutamicum S9114, a strain for industrial production of glutamate

Here we report the genome sequence of Corynebacterium glutamicum S9114, an industrial producer widely used in production of glutamate in China. Preliminary comparison with the sequences of the Corynebacterium glutamicum strains ATCC 13032 and R revealed some notable mutagenesis that might be related to the high yield of glutamate.     

Antiasthmatic drugs targeting the cysteinyl leukotriene receptor 1 alleviate central nervous system inflammatory cell infiltration and pathogenesis of experimental autoimmune encephalomyelitis

Cysteinyl leukotrienes (CysLTs) are potent proinflammatory mediators and are considered to play a key role in inflammatory diseases such as asthma. Antagonists targeting the receptor of CysLTs (CysLT1) are currently used as antiasthmatic drugs. CysLTs have also been implicated in other inflammatory reactions. In this study, we report that in experimental autoimmune encephalomyelitis animals, CysLT1 is upregulated in immune tissue and the spinal cord, and CysLT levels in the blood and cerebrospinal fluid are also higher than in normal mice. Two clinically used antiasthma drugs, montelukast and zafirlukast, both targeting CysLT1, effectively block the CNS infiltration of inflammatory cells and thus reduce the incidence, peak severity, and cumulative clinical scores. Further study indicated that CysLT1 signaling does not affect the differentiation of pathogenic T helper cells. It might affect the pathogenesis of experimental autoimmune encephalomyelitis by increasing the secretion of IL-17 from myelin oligodendrocyte glycoprotein-specific T cells, increasing the permeability of the blood-brain barrier and inducing chemotaxis of T cells. These effects can be blocked by CysLT1 antagonists. Our findings indicate that the antiasthmatic drugs against CysLT1 can also be used to treat multiple sclerosis.