Identification of a Novel Gene for Biosynthesis of a Bacteroid-Specific Electron Carrier Menaquinone

Ubiquinone (UQ) has been considered as an electron mediator in electron transfer that generates ATP in Rhizobium under both free-living and symbiosis conditions. When mutated, the dmtH gene has a symbiotic phenotype of forming ineffective nodules on Astragalus sinicus. The gene was isolated from a Mesorhizobium huakuii 7653R transposon-inserted mutant library. The DNA sequence and conserved protein domain analyses revealed that dmtH encodes demethylmenaquinone (DMK) methyltransferase, which catalyzes the terminal step of menaquinone (MK) biosynthesis. Comparative analysis indicated that dmtH homologs were present in only a few Rhizobia. Real-time quantitative PCR showed dmtH is a bacteroid-specific gene. The highest expression was seen at 25 days after inoculation of strain 7653R. Gene disruption and complementation tests demonstrated that the dmtH gene was essential for bacteroid development and symbiotic nitrogen fixation ability. MK and UQ were extracted from the wild type strain 7653R and mutant strain HK116. MK-7 was accumulated under microaerobic condition and UQ-10 was accumulated under aerobic condition in M. huakuii 7653R. The predicted function of DmtH protein was confirmed by the measurement of methyltransferase activity in vitro. These results revealed that MK-7 was used as an electron carrier instead of UQ in M. huakuii 7653R bacteroids

Development of a thiophene derivative modified LDH coating for Mg alloy corrosion protection.

A new thiophene derivative corrosion inhibitor (CI) was developed to functionalize the layered double hydroxide (LDH) primer on Mg alloy to enhance corrosion protection. Compared with bare LDH coating, the composite coatings consisting of a MgAl-LDH primer and an outer CI layer showed highly compact surface structures without large pores and gaps, thereby indicating the enhanced capability to resist the penetration of corrosive species. Electrochemical tests revealed that the MgAl-LDH film modified with the newly synthesized CI exhibited higher charge transfer resistance and lower corrosion current density than films modified with commercial CIs. The highest enhancement in corrosion resistance was linked to the film's ability to repair physical damage by forming precipitates through chemical complexation and adsorption of the CIs. These findings open up new opportunities for the design and synthesis of a thiophene-contained inhibitor to modify LDH films and to obtain a composite coating with superior corrosion protection

Structural determination of the complement inhibitory domain of Borrelia burgdorferi BBK32 provides insight into classical pathway complement evasion by Lyme disease spirochetes

The carboxy-terminal domain of the BBK32 protein from Borrelia burgdorferi sensu stricto, termed BBK32-C, binds and inhibits the initiating serine protease of the human classical complement pathway, C1r. In this study we investigated the function of BBK32 orthologues of the Lyme-associated Borrelia burgdorferi sensu lato complex, designated BAD16 from B. afzelii strain PGau and BGD19 from B. garinii strain IP90. Our data show that B. afzelii BAD16-C exhibits BBK32-C-like activities in all assays tested, including high-affinity binding to purified C1r protease and C1 complex, and potent inhibition of the classical complement pathway. Recombinant B. garinii BGD19-C also bound C1 and C1r with high-affinity yet exhibited significantly reduced in vitro complement inhibitory activities relative to BBK32-C or BAD16-C. Interestingly, natively produced BGD19 weakly recognized C1r relative to BBK32 and BAD16 and, unlike these proteins, BGD19 did not confer significant protection from serum killing. Site-directed mutagenesis was performed to convert BBK32-C to resemble BGD19-C at three residue positions that are identical between BBK32 and BAD16 but different in BGD19. The resulting chimeric protein was designated BXK32-C and this BBK32-C variant mimicked the properties observed for BGD19-C. To query the disparate complement inhibitory activities of BBK32 orthologues, the crystal structure of BBK32-C was solved to 1.7Ã… limiting resolution. BBK32-C adopts an anti-parallel four-helix bundle fold with a fifth alpha-helix protruding from the helical core. The structure revealed that the three residues targeted in the BXK32-C chimera are surface-exposed, further supporting their potential relevance in C1r binding and inhibition. Additional binding assays showed that BBK32-C only recognized C1r fragments containing the serine protease domain. The structure-function studies reported here improve our understanding of how BBK32 recognizes and inhibits C1r and provide new insight into complement evasion mechanisms of Lyme-associated spirochetes of the B. burgdorferi sensu lato complex

Independent modulation of individual genomic component transcription and a cis-acting element related to high transcriptional activity in a multipartite DNA virus

Background: The genome of Banana bunchy top virus (BBTV) consists of at least six circular, single-stranded DNA components of 1kb in length. Some BBTV isolates may also carry satellite DNA molecules that are not essential for BBTV infection. The relation between multipartite DNA virus replication and their transcriptional levels and the underlying mechanism remain unclear. Results: To understand the coordinated replication and transcription of the multiple genomic components, the absolute amounts of each BBTV DNA component were measured by real-time PCR (qPCR), and their transcriptional levels were determined by RNAseq and reverse transcription-qPCR (qRT-PCR). Significant differences were found in the absolute amounts of individual BBTV genomic components. Transcriptional levels of each BBTV genomic component obtained from the RNAseq data matched closely to those obtained from qRT-PCR, but did not correspond to the absolute amount of each DNA component. The ratio of transcript over DNA copies ranged from 46.21 to 1059.44%, which was possibly regulated by the promoter region in the intergenic region of each component. To further determine this speculation, the promoter region of the DNA-S, -M or -N was constructed to the upstream of green fluorescent protein (GFP) gene for transient expression by agrobacterium-mediated transformation method. The qRT-PCR showed the highest transcriptional activity was promoted by DNA-N promoter, about 386.58% activity comparing with CaMV 35S promoter. Confocal microscopy observation showed that the intensity of green fluorescence was corresponding to that of qRT-PCR. Conclusions: Our data clearly showed that BBTV was able to control the transcriptional level of each DNA component independently by through the promoter sequences in the intergenic region. Moreover, a cis-acting element from DNA-N component had a high transcriptional activity.National Natural Science Foundation of China [31401709]; Hainan Provincial Natural Science Foundation [20153130]; Central Public-interest Scientific Institution Basal Research Fund for Chinese Academy of Tropical Agricultural Sciences [19CXTD-33]; Young Elite Scientists Sponsorship Program, CSTC [CSTC-QN201704]Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

A STUDY ON THE EFFECT OF RESVERATROL ON LIPID METABOLISM IN HYPERLIPIDEMIC MICE

Background: The content of resveratrol is relatively high in Polygonum cuspidatum Sieb. et Zucc., and the resveratrol has the effect of blood vessel dilating, microcirculation improving, platelet aggregation inhibiting and anti-cancer. The objective of this paper was to study the effect of resveratrol on lipid metabolism in hyperlipidemia mice. Materials and Methods: Through the establishment of an experimental mouse model of hyperlipidemia, the effect of resveratrol on change in total cholesterol (TC), triglyceride (TG), high density lipoprotein cholesterol (HDL-c), and low-density lipoprotein cholesterol (LDL-c) levels in mouse serum were determined. Results: Resveratrol group can apparently reduce TC, TG, LDL-c and AI of hyperlipidemic mice in a dose effect manner. Conclusion: We concluded that resveratrol can effectively reduce blood lipid levels of hyperlipidemic mice

Ameliorating Adriamycin-Induced Chronic Kidney Disease in Rats by Orally Administrated Cardiotoxin from Naja naja atra

Previous studies reported the oral administration of Naja naja atra venom (NNAV) reduced adriamycin-induced chronic kidney damage. This study investigated the effects of intragastric administrated cardiotoxin from Naja naja atra venom on chronic kidney disease in rats. Wistar rats were injected with adriamycin (ADR; 6 mg/kg body weight) via the tail vein to induce chronic kidney disease. The cardiotoxin was administrated daily by intragastric injection at doses of 45, 90, and 180 μg/kg body weight until the end of the protocol. The rats were placed in metabolic cages for 24 hours to collect urine, for determination of proteinuria, once a week. After 6 weeks, the rats were sacrificed to determine serum profiles relevant to chronic kidney disease, including albumin, total cholesterol, phosphorus, blood urea nitrogen, and serum creatinine. Kidney histology was examined with hematoxylin and eosin, periodic acid-Schiff, and Masson’s trichrome staining. The levels of kidney podocin were analyzed by Western blot analysis and immunofluorescence. We found that cardiotoxin reduced proteinuria and can improve biological parameters in the adriamycin-induced kidney disease model. Cardiotoxin also reduced adriamycin-induced kidney pathology, suggesting that cardiotoxin is an active component of NNAV for ameliorating adriamycin-induced kidney damage and may have a potential therapeutic value on chronic kidney disease