Pathogen Diagnosis Value of Nanopore Sequencing in Severe Hospital-Acquired Pneumonia Patients

Background

Next-generation sequencing of the metagenome (mNGS) is increasingly used in pathogen diagnosis for infectious diseases due to its short detection time. The time for Oxford Nanopore Technologies (ONT) sequencing-based etiology detection is further shortened compared with that of mNGS, but only a few studies have verified the time advantage and accuracy of ONT sequencing for etiology diagnosis. In 2022, a study confirmed that there was no significant difference in sensitivity and specificity between ONT and mNGS in suspected community-acquired pneumonia patients, which there was no clinical study verified in patients with SHAP.

Methods

From October 24 to November 20, 2022, 10 patients with severe hospital-acquired pneumonia (SHAP) in the Nanfang Hospital intensive care unit (ICU) were prospectively enrolled. Bronchoalveolar lavage fluid (BALF) was collected for ONT sequencing, mNGS, and traditional culture. The differences in pathogen detection time and diagnostic agreement among ONT sequencing, mNGS, traditional culture method, and clinical composite diagnosis were compared.

Results

Compared with mNGS and the traditional culture method, ONT sequencing had a significant advantage in pathogen detection time (9.6±0.7 h versus 24.7±2.7 h versus 132±58 h, P <0.05). The agreement rate between ONT sequencing and the clinical composite diagnosis was 73.3% (kappa value=0.737, P <0.05).

Conclusion

ONT sequencing has a potential advantage for rapidly identifying pathogens.

[Reliability and validity of the Chinese version of the test of the adherence to inhalers (TAI)]

Objectives: To evaluate the reliability and validity of the Chinese version of the test of the adherence to inhalers (TAI) in Chinese patients with chronic airway disease. Methods: Based on the English version of TAI, the items of the Chinese version of TAI were determined after forward-backward translation and cultural adaption. Totally, 165 patients with chronic obstructive pulmonary disease (COPD) and asthma were enrolled from Respiratory Clinic of the Second Xiangya Hospital of Central South University from July to November 2021, and a questionnaire survey was conducted using the Chinese version of TAI and the Morisky medication adherence scale 8-item version (MMAS-8). The content validity of the scale was expressed by content validity index (CVI) and the construct validity was analyzed by exploratory factor analysis (EFA). The convergence validity was evaluated by Pearson correlation analysis. The reliability of the scale was expressed by Cronbach's α coefficient, the split-half reliability and test-retest reliability. Results: The CVI was 0.966. There were 10 items in total. Two factors were extracted from the Chinese version of TAI and the cumulative variance contribution rate was 57.236%. The load value of each item was more than 0.400 and the factor attribution of the item was consistent with the original scale. The total score of the Chinese version of TAI was positively correlated with the total score of the MMAS-8(r=0.835,P<0.001). The Cronbach's α of the overall scale was 0.843, the Guttman's half-reliability coefficient was 0.796 and the test-retest reliability was 0.884 (P<0.001), respectively. Conclusions: The Chinese version of TAI has good reliability and validity, which may be a reliable tool for evaluating the adherence to inhalers of patients with chronic airway disease in China.

miR-27b-3p Improved High Glucose-Induced Spermatogenic Cell Damage via Regulating Gfpt1/HBP Signaling

INTRODUCTION

Diabetes mellitus (DM)-induced testicular damage is characterized by abnormal apoptosis of spermatogenic cells. Here, we clarified the roles and the molecular mechanism of microRNA (miR)-27b-3p in high glucose (HG)-induced spermatogenic cell damage.

METHODS

GC-1 spg cells were treated with 30 mmol/L glucose for 24 h. Cell viability was assessed by 2.3 3-(4, 5-dimethylthiazolyl2)-2, 5-diphenyltetrazolium bromide (MTT) assay. And, levels of O-linked N-acetylglucosamine (OGT), apoptosis-related proteins, and autophagy-related proteins were evaluated using Western blot. Levels of tumor necrosis factor-α (TNF-α), IL-1β, IL-6, and UDP-N-acetylglucosamine (UDP-GlcNAc) were assessed by enzyme linked immunosorbent (ELISA) assay. Levels of reactive oxygen species (ROS), malonic dialdehyde (MDA) and activity of superoxide dismutase (SOD) in cells were determined using kits. Cell apoptosis was determined using flow cytometry assay. Besides, dual luciferase reporter assay was employed to verify the binding relationship between miR-27b-3p and glutamine-fructose-6-phosphate transaminase 1 (Gfpt1).

RESULTS

miR-27b-3p was markedly downregulated in HG-treated GC-1 spg cells. HG treatment caused decreased cell viability, increased oxidative stress and inflammation, and induced autophagy and apoptosis, which were abolished by miR-27b-3p overexpression. miR-27b-3p suppressed the activation of hexosamine biosynthetic pathway (HBP) signaling in HG-treated spermatogenic cells. miR-27b-3p directly bound to Gfpt1 and negatively regulated its expression.

CONCLUSION

miR-27b-3p could improve HG-induced spermatogenic cell damage via regulating Gfpt1/HBP signaling, providing a new treatment strategy for the treatment of DM-induced testicular damage.

The interaction between C/EBPβ and TFAM promotes acute kidney injury via regulating NLRP3 inflammasome-mediated pyroptosis

Sepsis-induced inflammatory damage is a crucial cause of acute kidney injury (AKI), and AKI is an ecumenical fearful complication in approximately half of patients with sepsis. CCAAT/enhancer-binding protein β (C/EBPβ) plays roles in regulating acute phase responses and inflammation. However, the role and mechanism of C/EBPβ in AKI are unclear. LPS combined with ATP-treated renal epithelial cells HK2 and cecal ligation-peferation (CLP)-mice were used as models of AKI in vitro and in vivo. Cell damage, the secretion of interleukin-1 beta (IL-1β), IL-18 and cysteinyl aspartate specific proteinase 1 (caspase-1) activity were tested by LDH, ELISA assay and flow cytometry analysis, respectively. The expression levels of TFAM, C/EBPβ, and pyroptosis-related molecules were tested by qRT-PCR and Western blotting. Chromatin immunoprecipitation (ChIP) assessed the interaction between C/EBPβ with TFAM. Hematoxylin-Eosin (H&E) staining detected pathological changes of kidney tissues, and immunohistochemistry measured TFAM and C/EBPβ in mice kidney tissues. C/EBPβ or TFAM were up-regulated in LPS combined with ATP -induced HK2 cells. Knockdown of C/EBPβ could suppress cell injury and the secretion of IL-1β and IL-18 induced by LPS combined with ATP. Furthermore, C/EBPβ up-regulated the expression levels of TFAM via directly binding to TFAM promoter. Overexpression of TFAM reversed the effects of C/EBPβ deficiency on pyroptosis. Knockdown of C/EBPβ could inhibit NLRP3 inflammasome-mediated caspase-1 signaling pathway by inactivating TFAM/RAGE pathway. It was further confirmed in the AKI mice that C/EBPβ and TFAM promoted AKI by activating NLRP3-mediated pyroptosis. The interaction of between C/EBPβ and TFAM facilitated pyroptosis by activating NLRP3/caspase-1 signal axis, thereby promoting the occurrence of AKI.

Involvement of phosphatase and tensin homolog-induced putative kinase 1-Parkin-mediated mitophagy in septic acute kidney injury

BACKGROUND

Studies have reported mitophagy activation in renal tubular epithelial cells (RTECs) in acute kidney injury (AKI). Phosphatase and tensin homolog-induced putative kinase 1 (PINK1) and E3 ubiquitin-protein ligase Parkin are involved in mitophagy regulation; however, little is known about the role of PINK1-Parkin mitophagy in septic AKI. Here we investigated whether the PINK1-Parkin mitophagy pathway is involved in septic AKI and its effects on cell apoptosis in vitro and on renal functions in vivo.

METHODS

Mitophagy-related gene expression was determined using Western blot assay in human RTEC cell line HK-2 stimulated with bacterial lipopolysaccharide (LPS) and in RTECs from septic AKI rats induced by cecal ligation and perforation (CLP). Autophagy-related ultrastructural features in rat RTECs were observed using electron microscopy. Gain- and loss-of-function approaches were performed to investigate the role of the PINK1-Parkin pathway in HK-2 cell mitophagy. Autophagy activators and inhibitors were used to assess the effects of mitophagy modulation on cell apoptosis in vitro and on renal functions in vivo.

RESULTS

LPS stimulation could significantly induce LC3-II and BECN-1 protein expression (LC3-II: 1.72 ± 0.05 vs. 1.00 ± 0.05, P < 0.05; BECN-1: 5.33 ± 0.57 vs. 1.00 ± 0.14, P < 0.05) at 4 h in vitro. Similarly, LC3-II, and BECN-1 protein levels were significantly increased and peaked at 2 h after CLP (LC3-II: 3.33 ± 0.12 vs. 1.03 ± 0.15, P < 0.05; BECN-1: 1.57 ± 0.26 vs. 1.02 ± 0.11, P < 0.05) in vivo compared with those after sham operation. Mitochondrial deformation and mitolysosome-mediated mitochondria clearance were observed in RTECs from septic rats. PINK1 knockdown significantly attenuated LC3-II protein expression (1.35 ± 0.21 vs. 2.38 ± 0.22, P < 0.05), whereas PINK1 overexpression markedly enhanced LC3-II protein expression (2.07 ± 0.21 vs. 1.29 ± 0.19, P < 0.05) compared with LPS-stimulated HK-2 cells. LPS-induced proapoptotic protein expression remained unchanged in autophagy activator-treated HK-2 cells and was significantly attenuated in PINK1-overexpressing cells, but was remarkably upregulated in autophagy inhibitor-treated and in PINK1-depleted cells. Consistent results were observed in flow cytometric apoptosis assay and in renal function indicators in rats.

CONCLUSION

PINK1-Parkin-mediated mitophagy might play a protective role in septic AKI, serving as a potential therapeutic target for septic AKI.

Upregulation of Mitochondrial Transcription Factor A Promotes the Repairment of Renal Tubular Epithelial Cells in Sepsis by Inhibiting Reactive Oxygen Species-Mediated Toll-Like Receptor 4/p38MAPK Signaling

BACKGROUND

Mitochondrial transcription factor A (TFAM) plays multiple pathophysiologic roles in mitochondrial DNA (mtDNA) maintenance. However, the role of TFAM in sepsis-induced acute kidney injury (AKI) remains largely unknown.

METHODS

Lipopolysaccharide (LPS) treatment of HK-2 cells mimics the in vitro model of AKI inflammation. pcDNA3.1 plasmid was used to construct pcDNA3.1-TFAM. sh-TFAM-543, sh-TFAM-717, sh-TFAM-765, sh-TFAM-904 and pcDNA3.1-TFAM were transfected into HK-2 cells using Lipofectamine 2000. MtDNA transcriptional levels were detected by quantitative real-time polymerase chain reaction (qRT-PCR). 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide (MTT) assay was performed to assess the cell viability. Changes in reactive oxygen species (ROS) and mitochondrial membrane potential in HK-2 cells were detected using the corresponding kits. Immunofluorescence experiment was used to investigate the displacement of TFAM. mRNA and protein expression levels of TFAM and its related genes were measured by qRT-PCR and western blot respectively. Mice in sepsis were administered cecal ligation and puncture surgery.

RESULTS

LPS treatment was a non-lethal influencing factor, leading to the upregulation of ROS levels and downregulation of mtDNA copy number and NADH dehydrogenase subunit-1 (ND1) expression, and caused damage to the mitochondria. As the LPS treatment time increased, TFAM was displaced from the periphery of the nucleus to cytoplasm. TFAM reduced ROS and P38MAPK levels by inhibiting toll-like receptor 4 (TLR4) expression, ultimately inhibiting inflammation and repairing mtDNA.

CONCLUSIONS

Our results indicate that TFAM repairs mtDNA by blocking the TLR4/ROS/P38MAPK signaling pathway in inflammatory cells, thereby repairing septic tubular epithelial cells, and TFAM may serve as a new target for sepsis therapy.

MicroRNA‑132 mediates proliferation and migration of pulmonary smooth muscle cells via targeting PTEN

Pulmonary arterial hypertension (PAH) is a severe and progressive disease characterized by the remodeling of small pulmonary arteries. The aberrant proliferation of pulmonary arterial smooth muscle cells (PASMCs) is the primary feature of PAH. MicroRNA (miR)‑132 has been demonstrated to inhibit the proliferation of vascular smooth muscle cells and repress neointimal formation. Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a direct target of miR‑132 that has been revealed to be involved in the development of PAH. However, the role of miR‑132 in PAH remains unclear. The present study demonstrated that miR‑132 expression was upregulated in monocrotaline‑induced PAH rats and platelet‑derived growth factor‑induced PASMCs. In addition, treatment of PASMCs with miR‑132 mimics inhibited their proliferation, whereas miR‑132 inhibition exhibited the opposite effects. Furthermore, miR‑132 mimics promoted cell migration and maintained the PASMC contractile phenotype. Finally, the expression levels of PTEN were significantly decreased in PAH and PASMCs treated with miR‑132 mimics. Taken collectively, the data suggested that miR‑132 regulated PASMC function via PTEN and that it may be used as a potential target for the treatment of PAH.

In vivo and in vitro anti-sepsis effects of physcion 8-O-β-glucopyranoside extracted from Rumex japonicus

The present study was designed to investigate the anti-sepsis effects of physcion 8-O-β-glucopyranoside (POG) isolated from Rumex japonicas and explore its possible pharmacological mechanisms. POG was extracted from R. japonicas by bioactivity-guided isolation with the anti-sepsis agents. Survival analysis in septic mouse induced by LPS and heat-killed Escherichia coli were used to evaluate the protective effect of POG (40 mg·kg^-1, i.p.) on sepsis. Cytokines including TNF-α, IL-1β and IL-6 in RAW 264.7 cells induced by LPS (100 ng·mL^-1) were determined by ELISA. In addition, the proteins expressions of TLR2 and TLR4 were determined by Western blotting assay. Our results demonstrated that POG (40 mg·kg^-1, i.p.) possessed significant protective activity on the endotoxemic mice. The POG treatment (20, 40, and 80 μg·mL^-1) significantly decreased the TNF-α, IL-1β and IL-6 induced by LPS (P < 0.01) in a concentration-dependent manner. Furthermore, the TLR4 and TLR2 proteins were also down-regulated by POG at 20 (P < 0.01), 40 (P < 0.01), and 80 μg·mL^-1 (P < 0.01). The present study demonstrated that the POG extracted from R. japonicas possessed significant anti-sepsis effect on endotoxemic mice, and can be developed as a novel drug for treating sepsis in the future.

The Transcriptome Study of Subtype M2 Acute Myeloblastic Leukemia

Our objective is to explore the tumor-specific mutated genes by transcriptome sequencing of patients with acute myeloblastic leukemia. 96 patients with subtype M2 acute myeloid leukemia (AML), admitted during January 2007 to January 2012, were selected. Bone marrow and peripheral blood samples from the patients after the first visit and the patients who were improved or alleviated, were subjected to high-throughput sequencing to compare the gene expression. The single nucleotide mutation related to subtype M2 AML was detected. Meanwhile, real-time fluorescent quantitation RT-PCR was used to detect the AML1/ETO fusion gene and its correlation with prognosis after treatment. Among 96 patients, AML1-ETO fusion gene was positive in 52 cases, the positive rate was 54.17 %. The complete relief (CR) rate of AML1-ETO fusion gene positive patients was 84.62 %, and the CR rate of AML1/ETO fusion gene negative patients was 77.27 %; the CR rate of AML1-ETO positive patients was higher than that of patients without the fusion gene, however there was no statistical difference. In the analysis of recurrent gene mutation in AML-M2 patients, IDH2, ASXL1, TET2, JAK1 and JAK2 gene expressions were not significantly different before treatment and after CR, however, IDHI, JAK3, ABL1 and BCR gene expressions were significantly different. In the study of transcriptome in AML-M2 patients, high-throughput sequencing could effectively detect the difference of the gene expression before treatment and after CR. Furthermore, positive expression of AML1-ETO fusion gene had effect on the prognosis of patients.

Spironolactone prevents dietary-induced metabolic syndrome by inhibiting PI3-K/Akt and p38MAPK signaling pathways

OBJECTIVES

Aim of the study is to evaluate the impact of spironolactone (SPL) on indexes of metabolic syndrome (MS) and further investigate the mechanisms underlying its protective effects.

METHODS

A rat model of MS was established by administering a fat- and salt-enriched diet (FS diet). The occurrence of MS was examined by measurement of blood pressure (BP), aldosterone (ALD) content, blood lipid (BL), glucose and insulin levels. Homeostasis model assessment of insulin resistance (HOMA-IR) was calculated. Pancreatic gland tissue injury was assessed by β-cell apoptosis. Mineralocorticoid receptor (MR) activity, phosphatidylinositol 3- kinase/Akt (PI3-K/Akt), and phosphorylation of p38MAPK (Pp38MAPK) in pancreatic gland tissue were evaluated by western blot analysis.

RESULTS

SPL prevented hypertension, and dyslipidemia during MS induced by the intake of FS diet, but had no effect on K+ and Na+ disturbances. Furthermore, SPL significantly attenuated ALD and MR expression levels after FS diet. Finally, SPL inhibited phosphorylation protein kinase B (p- PKB) activation in the pancreatic gland tissue, a downstream target of PI3-K, and phosphorylation of p38MAPK pathway, critical for cellular apoptosis.

CONCLUSIONS

This study demonstrates that SPL exerts a protective effect on hypertension and dyslipidemia. This protective effect may depend, at least in part, on MAPK and PI3-K pathways.

Genetic variation and differentiation of Gekko gecko from different populations based on mitochondrial cytochrome b gene sequences and karyotypes

Black-spotted and red-spotted tokay geckos are distributed in different regions and have significant differences in morphological appearance, but have been regarded as the same species, Gekko gecko, in taxonomy. To determine whether black-spotted and red-spotted tokay geckos are genetically differentiated, we sequenced the entire mitochondrial cytochrome b gene (1147 bp) from 110 individuals of Gekko gecko collected in 11 areas including Guangxi China, Yunnan China, Vietnam, and Laos. In addition, we performed karyotypic analyses of black-spotted tokay geckos from Guangxi China and red-spotted tokay geckos from Laos. These phylogenetic analyses showed that black-spotted and red-spotted tokay geckos are divided into two branches in molecular phylogenetic trees. The average genetic distances are as follows: 0.12-0.47% among six haplotypes in the black-spotted tokay gecko group, 0.12-1.66% among five haplotypes in the red-spotted tokay gecko group, and 8.76-9.18% between the black-spotted and red-spotted tokay geckos, respectively. The karyotypic analyses showed that the karyotype formula is 2n = 38 = 8m + 2sm + 2st + 26t in red-spotted tokay geckos from Laos compared with 2n = 38 = 8m + 2sm + 28t in black-spotted tokay geckos from Guangxi China. The differences in these two kinds of karyotypes were detected on the 15th chromosome. The clear differences in genetic levels between black-spotted and red-spotted tokay geckos suggest a significant level of genetic differentiation between the two.

The complete mitochondrial genome of Chrysolophus pictus (Galliformes: Phasianidae) and a phylogenetic analysis with related species

The 16,678 bp mitochondrial genome of the Chrysolophus pictus has been sequenced in this paper. To determine the phylogentic position of C. pictus with related species within Phasianidae, the phylogenetic tree was reconstructed with the concatenated nucleotide dataset of the 12 heavy-strand-encoded protein genes. The phylogenetic analysis was carried out using maximum parsimony (MP) and Bayesian inference (BI) methods. MP and BI phylogenetic trees here showed similar topology and consistently suggested that C. pictus shared a close relationship with Phasianus versicolor. The results also showed that the Meleagris gallopavo possessed a basal phylogenetic position within Phasianidae, which may imply that it should be classified into the Phasianidae.

Theory of nitride oxide adsorption on transition metal (111) surfaces: a first-principles investigation

In this work, we report a density functional theory study of nitric oxide (NO) adsorption on close-packed transition metal (TM) Rh(111), Ir(111), Pd(111) and Pt(111) surfaces in terms of adsorption sites, binding mechanism and charge transfer at a coverage of Theta(NO) = 0.25, 0.50, 0.75 monolayer (ML). Based on our study, an unified picture for the interaction between NO and TM(111) and site preference is established, and valuable insights are obtained. At low coverage (0.25 ML), we find that the interaction of NO/TM(111) is determined by an electron donation and back-donation process via the interplay between NO 5sigma/2pi* and TM d-bands. The extent of the donation and back-donation depends critically on the coordination number (adsorption sites) and TM d-band filling, and plays an essential role for NO adsorption on TM surfaces. DFT calculations shows that for TMs with high d-band filling such as Pd and Pt, hollow-site NO is energetically the most favorable, and top-site NO prefers to tilt away from the normal direction. While for TMs with low d-band filling (Rh and Ir), top-site NO perpendicular to the surfaces is energetically most favorable. Electronic structure analysis show that irrespective of the TM and adsorption site, there is a net charge transfer from the substrate to the adsorbate due to overwhelming back-donation from the TM substrate to the adsorbed NO molecules. The adsorption-induced change of the work function with respect to bare surfaces and dipole moment is however site dependent, and the work function increases for hollow-site NO, but decreases for top-site NO, because of differences in the charge redistribution. The interplay between the energetics, lateral interaction and charge transfer, which is element dependent, rationalizes the structural evolution of NO adsorption on TM(111) surfaces in the submonolayer regime.

[Relative bioavailability of effervescent tablet of potassium chloride in healthy volunteers]

AIM

To probe the approach by which the pharmacokinetics and relative bioavailability of endogenous medicinal substances can be studied.

METHODS

A randomized three-crossover study was performed in 18 healthy male volunteers. In two of the three study periods, a single 2 g dose of either effervescent tablet or common tablet of potassium chloride was administered; whereas in one of three periods no drug treatment was given to allow the nondrug-related (endogenous) potassium in urine to be determined. In each period the urine samples were collected at the following intervals: 0-2, 2-4, 4-6, 6-8, 8-10, 10-12, 12-24, 24-48 h after dose. Urine potassium was determined and the cumulative urine potassium-time data were fitted to a one-compartment model with first-order absorption. Bioavailability was represented by cumulative amount of potassium excreted in urine during 48 hours after drug administration and the bioequivalence of the two formulations was evaluated by analysis of variance and two one-sided t-test.

RESULTS

The pharmacokinetic parameters were as follows: effervescent tablet T1/2 ke = (6 +/- 5) h, T1/2 ka = (0.08 +/- 0.08) h, ku = (0.09 +/- 0.04) h-1, Xmax/f = (18 +/- 8) mmol; common tablet T1/2 ke = (8 +/- 5) h, T1/2 ka = (0.11 +/- 0.11) h, ku = (0.07 +/- 0.04) h-1, Xmax/f = (18 +/- 8) mmol. Relative bioavailability of effervescent tablet was 97.5% +/- 15.2% compared with common tablet.

CONCLUSION

The two formulations were of bioequivalence. The methods used in this study might be applicable to other similar studies involving endogenous medicinal substances.

Conformational correlation and coupled motion between residue A21 and B25 side chain observed in crystal structures of insulin mutants at position A21

The C-terminal residue of the insulin A chain is invariant and kept as asparagine in all known insulin molecules from hagfish through birds to mammals. To get information on the role of this conserved residue, which is still unclear, the three-dimensional structures of four human insulin mutants, A21 Asn-->Gly, A21 Asn-->Asp, A21 Asn-->Ala, and A21 Asn-->Gln DesB30, were determined by X-ray crystallography. The four mutants crystallize separately into two kinds (rhombohedral and cubic) of crystals. In the refined structures, conformational correlation and coupled motion between the A chain C-terminal residue A21 and the B25 side chain was observed, in contrast to the nearly unchanged general structures as compared with the native insulin structures in their respective crystals. A detailed analysis suggests that residue A21 can affect insulin receptor binding by interaction with the B25 side chain and the B chain C-terminal segment to assist the B25 side chain rearranging into the 'active' conformation.

Crystal structures of two alpha-like scorpion toxins: non-proline cis peptide bonds and implications for new binding site selectivity on the sodium channel

The crystal structures of two group III alpha-like toxins from the scorpion Buthus martensii Karsch, BmK M1 and BmK M4, were determined at 1.7 A and 1.3 A resolution and refined to R factors of 0.169 and 0.166, respectively. The first high-resolution structures of the alpha-like scorpion toxin show some striking features compared with structures of the "classical" alpha-toxin. Firstly, a non-proline cis peptide bond between residues 9 and 10 unusually occurs in the five-member reverse turn 8-12. Secondly, the cis peptide 9-10 mediates the spatial relationship between the turn 8-12 and the C-terminal stretch 58-64 through a pair of main-chain hydrogen bonds between residues 10 and 64 to form a unique tertiary arrangement which features the special orientation of the terminal residues 62-64. Finally, in consequence of the peculiar orientation of the C-terminal residues, the functional groups of Arg58, which are crucial for the toxin-receptor interaction, are exposed and accessible in BmK M1 and M4 rather than buried as in the classical alpha-toxins. Sequence alignment and characteristics analysis suggested that the above structural features observed in BmK M1 and M4 occur in all group III alpha-like toxins. Recently, some group III alpha-like toxins were demonstrated to occupy a receptor site different from the classical alpha-toxin. Therefore, the distinct structural features of BmK M1 and M4 presented here may provide the structural basis for the newly recognized toxin-receptor binding site selectivity. Besides, the non-proline cis peptide bonds found in these two structures play a role in the formation of the structural characteristics and in keeping accurate positions of the functionally crucial residues. This manifested a way to achieve high levels of molecular specificity and atomic precision through the strained backbone geometry.

Structure of an insulin dimer in an orthorhombic crystal: the structure analysis of a human insulin mutant (B9 Ser-->Glu)

The structure of human insulin mutant B9 (Ser-->Glu) was determined by an X-ray crystallographic method at 2.5 A resolution with an R factor of 0.165 under non-crystallographic restraints. The crystals were grown at low pH (<3.8) and belong to the orthorhombic P2(1)2(1)2(1) space group with unit-cell dimensions a = 44.54, b = 46.40, c = 51.85 A and one dimer per asymmetric unit without further aggregation. The structure in this crystal form can be regarded as a model for a discrete insulin dimer and displays the following features compared with the structure of 2Zn insulin. (i) The overall dimer is expanded and more symmetric. The two A chains are about 2 A more distant from each other, while the two B chains are about 0.8 A further apart. Both monomers are more similar to molecule 1 than molecule 2 of the 2Zn insulin dimer. (ii) The dimer structure is stabilized by protonation and neutralization of the carboxyl groups at lower pH and, in addition, by formation of a hydrogen-bond network among the side chains of residues GluB9, HisB13 and HisB10 on the dimer-forming surface of both monomers, resulting from a structural rearrangement. (iii) The B-chain amino-terminal segment is in an open state (O state), i.e. a state different from the well known R and T states found in the insulin hexamer. In the O state, the B-chain N-terminal segment is in an extended conformation and is detached from the rest of the molecule. This conformational state has also been observed in the monomeric crystal structure of despentapeptide (B26-B30) and desheptapeptide (B24-B30) insulin, as well as in the solution structure of an engineered insulin monomer. It suggests that the O state may be the characteristic conformation of insulin in lower aggregation forms and may be relevant to the formation of insulin fibrils. In addition, based on the crystallization process, the smallest possible building blocks of insulin crystal are also discussed.

Crystallization and preliminary crystallographic analyses of pokeweed antiviral protein from seeds

Pokeweed antiviral protein from seeds (PAP-S) is a ribosome inactivating protein which has lowest toxicity and highest inhibition activity as opposed to other pokeweed antiviral proteins and its three potential glycosylation sites (10, 44, 255) were shown to bind to N-acetylglucosamine. Good quality crystals of PAP-S were grown at high protein concentration (100 mg ml-1) and high temperature (306 K). The crystals have space group I222 and cell parameters a = 78.7, b = 85.2 and c = 93.0 A. An X-ray diffraction data set with resolution up to 1.8 A was collected. This high-resolution data will help to locate the sugars bound to the protein and provide accurate structural data for understanding structure-function relationships of PAP-S.

[The detection and study on enterotoxigenic Escherichia coli in China]

In this paper, some strains of ETEC were first detected from the stools of the patients with cholerae-like diarrhea in China in 1974. With a detected rate 36.48% of ETEC Detected rates weve 20.18% from patients with acute diarrhea, 19.74% from environment and sea foods. ETEC produced most of LT toxin in culture medium when the they were incubated at 37-42 degrees C for 4 days. When Rabbit ileal loop test (RILT) was performed with the culture of ETEC or with germ-free culture supernatant, a large quantity of intestinal fluid in response to LT was accumulated at 24 hour and showed positive reaction at every test. Similar results were qained by using 5 cm or 10 cm ileal loop of RILT for LT detectoing. Better effects were noticed through injection of 1.0-3.0 ml culture of ETEC or germ-free enterotoxin in per 5 cm ileal loop. LT could be destroyed by heating at > 50 degrees C or pH < 4.0.

Crystal structure of an acidic neurotoxin from scorpion Buthus martensii Karsch at 1.85 A resolution

The crystal structure of an acidic scorpion neurotoxin, BmK M8, purified from Chinese scorpion Buthus martensii Karsch (BmK), has been determined by the molecular replacement method. It is the first structure of an acidic alpha-scorpion neurotoxin reported so far. The crystals adopt a symmetry of space group P2(1) and contain one molecule per asymmetric unit. The structure has been refined to an R factor of 18.1% using reflection data in the range of 8 to 1.85 A resolution, with standard deviations from ideal geometry of 0.017 A and 2.43 degrees for bond length and angle, respectively. The 12 residues at the C terminus with unknown sequence were determined by crystallographic refinement. The refined model shows that the structural core, consisting of a motif beta alpha beta beta, is similar to that of toxin II from Androctonus australis Hector (AaH II) or Variant 3 from Centruroides sculpturatus Ewing (CsE V3). The three conformationally variable loops protruding from this structural core are different from that of AaH II, and especially from that of CsE V3. Compared with the most potent and basic alpha-toxin AaH II, the BmK M8 is a relatively inactive toxin (1100 times less active than AaH II) with an unusually low isoelectric point (pI 5.3). Sequence alignment of the two toxins shows a difference of 26 residues (40.6%). Among them four basic or neutral residues in AaH II, namely Val10, Lys28, Val55 and Gly59, are changed to acidic glutamate in BmK M8. The residues Glu10, Glu28 and Glu55 of BmK M8 are located on a surface (Face B), opposite the "conserved hydrophobic surface" (Face A). The latter is a functionally important area proposed by Fontecilla-Camps et al. Our observations suggest that in addition to Face A, Face B may also be involved in the biological activity of scorpion toxins. The structure of BmK M8 shows an evident conformational change of the alpha-amino group at the N terminus and a deorganization of Arg2 caused by the mutation D53A. These structural changes may also be responsible for the weak toxicity of BmK M8. In association with the information from chemical modifications, a multisite binding mode for toxin-receptor interaction and three "toxic regions" in relevance to the binding process, including Face A, Face B and Site C, are proposed. Face A, mainly consisting of Tyr5, 35, 47, the alpha-amino group, Arg2 and Asp3, may be more essential for the binding. Face B, mainly comprising conserved residues Tyr14, 21, Lys28 and Val55, may contribute to the high efficacy of the binding process and substitutions by acidic residues in this area could strongly weaken the toxic activity. Site C, formed by Lys58 and Arg62 at the C terminus and Arg41 and Tyr42 from loop 38-44, may be involved in binding site specificity.