PAQR9 regulates glucose homeostasis in diabetic mice and modulates insulin secretion in β cells in vitro under stress conditions

Progesterone and adipoQ receptor 9 (PAQR9) is an endoplasmic reticulum (ER)-localized membrane protein that is involved in protein quality control of ER by interacting with BAG6. One of the physiological functions of PAQR9 is regulation of fasting-induced ketogenesis and fatty acid oxidation in the liver via modulating protein degradation of PPARα. However, it is currently unknown whether or not PAQR9 impacts glucose homeostasis. We addressed this question using a Paqr9-deleted mouse model in which type 1 diabetes was induced by streptozotocin injection and type 2 diabetes was induced by high-fat diet (HFD) with streptozotocin injection. Paqr9 deletion improved hyperglycemia and glucose tolerance in both of the diabetic mouse models. In the pancreatic islets, Paqr9 deletion reduced apoptosis of β cells in type 2 diabetic mice. Paqr9 deletion also reduced HFD-induced hepatic steatosis and adiposity of white adipose tissue. In Min6 cells, overexpression of DUF3538 domain of BAG6 to block the interaction of PAQR9 with BAG6 was able to enhance glucose-stimulated insulin secretion upon treatment with inflammatory factors or thapsigargin, an ER stress inducer. Thapsigargin-induced ER stress markers were also reduced by overexpression of DUF3538 domain. Collectively, these results indicate that PAQR9 has a modulatory role in glucose homeostasis, associated with regulation on insulin secretion of β cells in vitro under stress conditions.

Bedaquiline for multidrug-resistant TB in paediatric patients

BACKGROUND:

TMC207-C211 (NCT02354014) is a Phase 2, open-label, multicentre, single-arm study to evaluate pharmacokinetics, safety/tolerability, antimycobacterial activity and dose selection of bedaquiline (BDQ) in children (birth to <18 years) with multidrug-resistant-TB (MDR-TB).

METHODS:

Patients received 24 weeks’ BDQ with an anti-MDR-TB background regimen (BR), followed by 96 weeks of safety follow-up. Results of the primary analysis are presented based on data up to 24 weeks for Cohort 1 (≥12–<18 years; approved adult tablet at the adult dosage) and Cohort 2 (≥5–<12 years; age-appropriate 20 mg tablet at half the adult dosage).

RESULTS:

Both cohorts had 15 patients, of whom respectively 53% and 40% of Cohort 1 and Cohort 2 children had confirmed/probable pulmonary MDR-TB. Most patients completed 24 weeks’ BDQ/BR treatment (Cohort 1: 93%; Cohort 2: 67%). Geometric mean BDQ area under the curve 168h values of 119,000 ng.h/mL (Cohort 1) and 118,000 ng.h/mL (Cohort 2) at Week 12 were within 60–140% (86,200–201,000 ng.h/mL) of adult target values. Few adverse event (AE) related discontinuations or serious AEs, andnoQTcF >460 ms during BDQ/BR treatment or deaths occurred. Of MGIT-evaluable patients, 6/8 (75%) Cohort 1 and 3/3 (100%) Cohort 2 culture converted.

CONCLUSION:

In children and adolescents aged ≥5–<18 years with MDR-TB, including pre-extensively drug-resistant-TB (pre-XDR-TB) or XDR-TB, 24 weeks of BDQ provided a comparable pharmacokinetic and safety profile to adults.

Icariin Inhibits Intestinal Inflammation of DSS-Induced Colitis Mice Through Modulating Intestinal Flora Abundance and Modulating p-p65/p65 Molecule

BACKGROUND

Ulcerative colitis, as a kind of inflammatory bowel disease (IBD) is characterized by abdominal pain. This study aimed to investigate the effect of icariin (ICA) on the intestinal microflora of colitis mice.

METHODS

Fifteen female C57BL/6 mice were randomly divided into the Control group, dextran sodium sulfate (DSS)-induced colitis (DSS) group, and ICA treatment (DSS+ICA) group. The severity of inflammation in DSS-induced colitis mice was evaluated using disease activity scoring (considering weight-loss percentage, stool-shape change, and stool-bleeding scoring). Pathological changes of mice intestinal tract were evaluated using hematoxylin-eosin (HE) staining. Serum levels of TNF-α and IL-6 were detected with enzyme-linked immunosorbent assay. Expressions of p65 and p-p65 (p-p65/p65 ratio) were analyzed using Western blot assay. 16S rDNA sequencing was used to analyze the abundance and composition of intestinal microflora.

RESULTS

Compared with DSS group, ICA significantly improved disease activity (P < .05) and reduced inflammatory damage of colon tissues (P < .05) in DSS-induced colitis mice. Compared with the DSS group, mice in the ICA group demonstrated significant weight and colon length (P < .05). ICA significantly inhibited expressions of IL-6 and TNF-α compared to the DSS group (P < .05). p-p65/ p65 ratio in the DSS + ICA group was remarkably enhanced compared to the DSS group (P < .05). ICA significantly reduced the proportion and activity of Bacteroides, Helicobacteraceae, Turicibacter, and significantly increased that of beneficial microflora (Lactobacillus, Lachnospiraceae, Akkermansia), so as improved damages of colon tissues.

CONCLUSION

ICA can improve intestinal flora abundance and composition of DSS-induced colitis mice, and inhibit tissue damage and inflammatory response through modulating the p-p65/p65 expression.

Household air pollution and personal exposure to nitrated and oxygenated polycyclic aromatics (PAHs) in rural households: Influence of household cooking energies

Residential solid fuels are widely consumed in rural China, contributing to severe household air pollution for many products of incomplete combustion, such as polycyclic aromatic hydrocarbons (PAHs) and their polar derivatives. In this study, concentrations of nitrated and oxygenated PAH derivatives (nPAHs and oPAHs) for household and personal air were measured and analyzed for influencing factors like smoking and cooking energy type. Concentrations of nPAHs and oPAHs in kitchens were higher than those in living rooms and in outdoor air. Exposure levels measured by personal samplers were lower than levels in indoor air, but higher than outdoor air levels. With increasing molecular weight, individual compounds tended to be more commonly partitioned to particulate matter (PM); moreover, higher molecular weight nPAHs and oPAHs were preferentially found in finer particles, suggesting a potential for increased health risks. Smoking behavior raised the concentrations of nPAHs and oPAHs in personal air significantly. People who cooked food also had higher personal exposures. Cooking and smoking have a significant interaction effect on personal exposure. Concentrations in kitchens and personal exposure to nPAHs and oPAHs for households using wood and peat were significantly higher than for those using electricity and liquid petroleum gas (LPG).

Monitoring wound healing of elastic cartilage using multiphoton microscopy

OBJECTIVE

To demonstrate the ability of multiphoton microscopy (MPM) for monitoring wound healing of elastic cartilage.

METHOD

In a rabbit ear model, four cartilage specimen groups at 1-day, 1-, 4-, 20-week healing time points as well as a normal elastic cartilage were examined with MPM without using labeling agents. MPM images at wound margins were obtained from specimens at different healing stages, compared with the Hematoxylin and Eosin (H&E) stained images. Image analysis was performed to characterize the collagen morphology for quantifying the wound healing progression of elastic cartilage.

RESULTS

MPM provided high-resolution images of elastic cartilage at varying depths. Comparisons of the images of specimens at different healing stages show obvious cell growth and matrix deposition. The results are consistent with the histological results. Moreover, quantitative analysis results show significant alteration in the collagen cavity size or collagen orientation index during wound healing of elastic cartilage, indicating the possibility to act as indicators for monitoring wound healing.

CONCLUSION

Our results suggested that MPM has the ability to monitor the wound healing progression of elastic cartilage, based on the visualization of cell growth and proliferation and quantitative characterization of collagen morphology during wound healing.

Nonlinear spectral imaging of human hypertrophic scar based on two-photon excited fluorescence and second-harmonic generation

BACKGROUND

A noninvasive method using microscopy and spectroscopy for analysing the morphology of collagen and elastin and their biochemical variations in skin tissue will enable better understanding of the pathophysiology of hypertrophic scars and facilitate improved clinical management and treatment of this disease.

OBJECTIVE

To obtain simultaneously microscopic images and spectra of collagen and elastin fibres in ex vivo skin tissues (normal skin and hypertrophic scar) using a nonlinear spectral imaging method, and to compare the morphological structure and spectral characteristics of collagen and elastin fibres in hypertrophic scar tissues with those of normal skin, to determine whether this approach has potential for in vivo assessment of the pathophysiology of human hypertrophic scars and for monitoring treatment responses as well as for tracking the process of development of hypertrophic scars in clinic.

METHODS

Ex vivo human skin specimens obtained from six patients aged from 10 to 50 years old who were undergoing skin plastic surgery were examined. Five patients had hypertrophic scar lesions and one patient had no scar lesion before we obtained his skin specimen. A total of 30 tissue section samples of 30 mum thickness were analysed by the use of a nonlinear spectral imaging system consisting of a femtosecond excitation light source, a high-throughput scanning inverted microscope, and a spectral imaging detection system. The high-contrast and high-resolution second harmonic generation (SHG) images of collagen and two-photon excited fluorescence (TPEF) images of elastin fibres in hypertrophic scar tissues and normal skin were acquired using the extracting channel tool of the system. The emission spectra were analysed using the image-guided spectral analysis method. The depth-dependent decay constant of the SHG signal and the image texture characteristics of hypertrophic scar tissue and normal skin were used to quantitatively assess the amount, distribution and orientation of their collagen and elastin components.

RESULTS

Our experiments and data analyses demonstrated apparent differences between hypertrophic scar tissue and normal skin in terms of their morphological structure and the spectral characteristics of collagen and elastin fibres. These differences can potentially be used to distinguish hypertrophic scar tissues from normal skin and to evaluate treatment responses.

CONCLUSIONS

All the measurements were performed in backscattering geometry and demonstrated that nonlinear spectral imaging has the ability to differentiate hypertrophic scar tissue from normal skin based on noninvasive SHG imaging, and TPEF imaging revealed the microstructure and spectral features of collagen and elastin fibres. With the advances in spectral imaging apparatus miniaturization, we have good reason to believe that this approach can become a valuable tool for the in vivo pathophysiology study of human skin hypertrophic scars and for assessing the treatment responses of this disfiguring disease in clinic. It can also be used to track the development of hypertrophic scars and to study wound healing processes in a noninvasive fashion without biopsy, fixation, sectioning and the use of exogenous dyes or stains.

Modulation of human cytomegalovirus immediate-early gene enhancer by mitogen-activated protein kinase kinase kinase-1

The immediate-early (IE) promoter of human cytomegalovirus (HCMV) constitutes a primary genetic switch, which determines the progression of viral infection. Earlier reports by others have shown mitogen-activated protein kinase kinase kinase-1 (MEKK1) to be able to up-regulate HCMV-IE promoter through downstream mitogen-activated protein kinase (MAPK) pathways. However, we noticed that the activation of the HCMV-IE promoter by constitutively active MEKK1 (MEKK1-TRU) might not be through the MAPK pathways. Using a HCMV-IE enhancer/promoter (- 522 to + 72) driving a luciferase reporter, we demonstrated that the downstream MAPK activation actually repressed the up-regulation of the promoter by MEKK1 in CHO-K1 and human 293 cells. We further found that the up-regulation of HCMV-IE promoter by MEKK1 could be in great extent suppressed by over-expression of IkappaBalpha. Deletion of the NFkappaB/rel sites in the HCMV-IE enhancer region by mutagenesis proportionally reduced the transcriptional activation by MEKK1-TRU, whereas deletion of the ATF/CREB binding sites or cyclic AMP response elements (CRE) had no effects. Furthermore, the NFkappaB/rel deletion mutant also showed repression on the basic transcription activity of the HCMV-IE promoter. Our results indicate that the NFkappaB/rel sites are not only responsible for the modulation of HCMV-IE enhancer activity by MEKK1 but also control the basic transcription activity of the HCMV-IE promoter. On the other hand, the four consensus CRE sites were found to have no function in the activation of the promoter by MEKK1.

Nonproteolytic role for the urokinase receptor in cellular migration in vivo

The urokinase receptor (uPAR) binds and localizes urokinase activity at cellular surfaces, facilitating fibrinolysis and cellular migration at sites of tissue injury. uPAR also participates in cellular signaling and regulates integrin-dependent adhesion and migration in vitro. We now report evidence that uPAR occupancy regulates cellular migration in vivo in the absence of functional urokinase. Recombinant murine KC (1.5 microg), a potent neutrophil chemoattractant, was delivered to the lungs of wild-type, urokinase-deficient or uPAR-deficient mice 18 h after intraperitoneal injection of 200 microg human immunoglobulin G (IgG) or a fusion protein composed of an amino-terminal receptor-binding fragment of urokinase and a human IgG Fc fragment (GFD-Fc). Whole lung lavage for recovery of leukocytes was performed 4 h later. KC treatment resulted in a 100-fold increase in lavage neutrophils. GFD-Fc injection resulted in >50% reduction in neutrophil influx in both wild-type and urokinase-deficient animals but had no effect on uPAR -/- mice. A concomitant reduction in alveolar protein leakage but no change in numbers of circulating neutrophils accompanied this attenuated inflammatory response. The reduction in neutrophil influx induced by GFD-Fc is thus related to uPAR occupancy and yet not due to disruption of uPAR-mediated proteolysis. These observations verify that protease-independent functions of uPAR operate in vivo and identify uPAR as a potential target for regulation of inflammatory processes characterized by neutrophil-mediated injury.

[FPMULTI--a software for multi-layer composition and thickness analysis and its applications]

Main features of FPMULTI, a software for analyzing composition and thickness of multi-layer samples simultaneously using XRF, are briefly described in this paper. Based on fundamental parameter method, the software has the capability of determining multi-layer samples containing up to 10 layers and 25 elements. Calibration standards can be bulk or multi-layer of pure element or multi-element standards. Application examples for tin-plates, hot dip galvanized zinc-plates and 'fingerprint-resistant' plates were given. FPMULTI is used to predict the relationship between intensities of different X-ray lines and the thickness first and then to analyze those samples. When using only few calibration standards, the results from FPMULTI are much better than those from linear regression method, and this reflects the advantages of the fundamental parameter approach.

Urokinase receptor antagonists: discovery and application to in vivo models of tumor growth

Urokinase receptor antagonists based on the growth factor domains of both human and murine urokinase which show sub-nanomolar affinities for their homologous receptors have been expressed as recombinant proteins. Further modification of these molecules by preparing fusions with the constant region of human IgG has led to molecules with high affinities and long in vivo half-lives. Smaller peptidic inhibitors have been obtained by a combination of bacteriophage display and peptide analog synthesis. All of these molecules inhibit the binding of the growth factor domain of uPA to the uPA receptor and enhance binding of the uPA receptor to vitronectin. Protein uPA receptor antagonists were tested in an in vivo tumor model using the human breast carcinoma MDAmb231 in immunodeficient mice. Both human and murine receptor antagonists showed significant inhibition of primary tumor growth, demonstrating that in vivo, both tumor and stromal cell uPA receptor dependent plasminogen activation can modulate tumor growth.

Effects of sulfhydryl regents on the activity of lambda Ser/Thr phosphoprotein phosphatase and inhibition of the enzyme by zinc ion

Sulfhydryl reagents, such as dithiothreitol (DTT), affected the activity of Ser/Thr phosphoprotein phosphatases. Addition of DTT to the assay buffer increased the affinity of lambda Ser/Thr phosphoprotein phosphatase (lambda-PPase) for its Mn2+ cofactor. On the other hand, the enzyme was found to be inactivated simply by dilution in Tris buffer. The inactivation could be completely prevented by the presence of DTT or Mn2+ in the buffer. Further studies showed that oxidation or reduction of cysteine residues in lambda-PPase may not be the cause of the change in the enzyme activity. Without exception, mutation of all cysteine residues in lambda-PPase to serine did not convert the enzyme into a thiol-insensitive mutant. By careful examination of the effects of different sulfhydryl reagents, metal ion cofactors and substrates on lambda-PPase, it was found that the role of sulfhydryl reagents was the chelation of small amounts of inhibitory metal ions, which were present in plastic laboratory ware, such as disposable cuvets and tubes, with prevention of the enzyme from inactivation. One of the main contaminants found in plastic cuvets was Zn2+, which is a potent inhibitor of lambda-PPase. The inhibition of lambda-PPase by Zn2+ was characterized. Pre-treatment of the enzyme (1-4 nM) with 1 microM of ZnCl2 almost completely inhibited the enzymatic activity in response to 2 mM Mn2+. However, no significant inhibition was found when the enzyme was added to the assay mixture containing 1 microM Zn2+ and 2 mM Mn2+ . This confirms the sensitivity of the holoenzyme to inhibitory metal ions in vitro. The kinetic analysis indicated that the inhibitory metal ion might compete with Mn2+ to bind to the active site of lambda-PPase. This was further supported by the mutation of metal cofactor binding amino acid residues of the enzyme. Mutants which have less affinity for Mn2+ are also less sensitive to Zn2+. Our results suggest that inhibitory metal ions may induce a different structural conformation for lambda-PPase.

Field studies on the preventive effect of oral artemether against schistosomal infection

OBJECTIVE

To study the preventive effect of oral artemether (Art) against schistosomal infection in the field.

METHODS

In Minglang District of Yiyang City, Hunan Province, there is an islet with embankment type endemic area in the southern Dongting Lake region. From August to October 1994 the residents who frequently contacted the infested water were selected for study and allocated to the Art group and the control group. About one month before the preventive Art administration, all the residents understudied were examined by stool hatching technique, and then treated orally with praziquantel at a single dose of 40 mg/kg in stool egg-negative residents and 50 mg/kg in stool egg-positive ones. In the Art group, the first dose of 6 mg/kg was given at the end of August, followed by 3 repeated doses every 15 days. Placebo (starch) was given to the control group at the same time as in the Art group. The preventive efficacy was evaluated by stool examination 25-32 days after the last medication.

RESULTS

In the Art group, 20 out of 365 studied residents became stool positive with an infection rate of 5.5%, while in the control group, 51 out of 376 studied residents were stool positive with an infection rate of 13.6%. The egg count per gram of feces (EPG) determined by the Kato-Katz method was 122 +/- 79 in the Art group and 681 +/- 909 in the control group. Meanwhile, two cases of acute schistosomiasis were found in the control group, but none was observed in the Art group. No apparent adverse side effect was seen during the treatment with Art.

CONCLUSION

Oral Art exhibited apparent preventive effect on the residents who contacted the infested water in schistosomiasis endemic area.

Effects of depletion of intracellular tetrahydrobiopterin in murine erythroleukemia cells

The biosynthesis of 6(R)-5,6,7,8-tetrahydrobiopterin (BH4) in murine erythroleukemia (MEL) cells is almost completely inhibited by 10 mM, 2,4-diamino-6-hydroxypyrimidine (DAHP), which targets GTP cyclohydrolase. The inhibition results in dephosphorylation of the retinoblastoma gene product, prolongation of the G1-phase in the cell cycle, and subsequent commitment to terminal differentiation of MEL cells. Reversal of the processes by repletion of cellular BH4 with biopterin-related compounds including BH4, 7,8-dihydrobiopterin (7,8-BH2), sepiapterin, and 7,8-dihydroneopterin has generated complicated results. Low micromolar exogenous pterin compounds had little or no effect. At 300 microM or higher, the synthesis of hemoglobin by DAHP-induced MEL cells is significantly inhibited by 7,8-dihydrobiopterin and sepiapterin. However, further cell cycle analysis shows that the inhibition of cell differentiation by 7,8-BH2 and sepiapterin may not be due to the reversal of cell proliferation. Inhibition of BH4 biosynthesis in MEL cells by inhibitors of sepiapterin reductase has also been studied. None of the inhibitors that were tested, including N-chloroacetyl-dopamine and N-acetylserotonin, which are specific for sepiapterin reductase, can block MEL cells in G1-phase or induce the cells to commit to terminal differentiation. Furthermore, inhibitors of sepiapterin reductase are found to reduce or to abolish hemoglobin synthesis in differentiating MEL cells induced by hexamethylene bisacetamide. The mechanism for this is not clear. Not all of the effects caused by the depletion of BH4 synthesis can be rescued by repletion of BH4. These results suggest that BH4 may not regulate proliferation or differentiation of MEL cells as previously thought. Its function in MEL cells is still not clear.

Study of the role of retinoblastoma protein in terminal differentiation of murine erythroleukemia cells

Hexamethylenebisacetamide-induced terminal differentiation of Friend virus-transformed murine erythroleukemia (MEL) cells can be inhibited by okadaic acid, an inhibitor of type 1 and type 2A protein phosphatases. The inhibition is shown to be correlated with prevention of dephosphorylation of retinoblastoma protein (pRB) in cells and bypass of G1 prolongation in the cell cycle. These results suggest that pRB-mediated G1 prolongation is necessary for MEL cells to commit to terminal differentiation. However, further experiments demonstrate that the simple cell cycle exit is not sufficient for commitment to terminal differentiation. Induction of dephosphorylation of pRB and subsequent G1 prolongation by forskolin does not lead MEL cells to differentiate. Additional pRB has been expressed in MEL cells by transfection with a neo-resistant plasmid containing RB cDNA under the control of a cytomegalovirus promoter. Exogenously expressed pRB is hyperphosphorylated in logarithmically growing MEL cells without any noticeable change in growth rate between the transfected cell line and the parental cell line. This result suggests that pRB in MEL cells is regulated by protein kinases and protein phosphatases and not by transcription.

[Field studies on preventive effect of artemether against infection with Schistosoma japonicum]

From August to October 1994, a field trial of preventive treatment with artemether (Art) was carried out in Minglang District of Yiyang City, Hunan Province, an islet with embankment type endemic area nearby southern Donting Lake region. The residents who frequently contacted with the infested water were selected for study and allocated to the Art group and the control group in reference to paired methods of randomization table. About one month before administration of Art, all residents under study were examined by stool hatching technique after nylon-bag concentration to determine the infection rate of each group, and then treated with praziquantel at a single dose of 40 mg/kg in stool egg-negative residents and 50 mg/kg in stool egg-positive ones. In Art group, the first dose of 6 mg/kg was given in late August, followed by repeated dosing every 15 days for 3 times. Placebo (starch) was given to the study residents in the control group at the same time as in Art group. The efficacy was evaluated by stool examination 25-32 days after the last medication. The results showed that after the preventive administration of Art, 20 out of 365 study residents in Art group revealed stool positive with an infection rate of 5.5%, while in the control group 51 out of 376 study residents showed stool positive with an infection rate of 13.6%. The difference between the two groups was statistically significant. Meantime, two cases of acute schistosomiasis were seen in the control group, but none was observed in Art group. The egg per gram of feces (EPG) determined with the Kato-Katz method was 122 +/- 79 (range 12-192) in Art group and 681 +/- 909 (range 12-2,760) in the control group. No apparent adverse side effect was seen during the treatment with Art, and no abnormal change in liver and renal function was detected after the last medication. The preliminary study indicates that application of the preventive administration of Art in the endemic area during the transmission season may effectively reduce both the infection rate and intensity of schistosomiasis.

Mutational analysis of a Ser/Thr phosphatase. Identification of residues important in phosphoesterase substrate binding and catalysis

The Ser/Thr phosphoprotein phosphatases (PPases) display similarities in amino acid sequence and biochemical properties. Most members of this family require transition metal ions for activity. The smallest family member, the bacteriophage lambda PPase (lambda-PPase), has been successfully overexpressed in Escherichia coli, purified, and characterized (Zhuo, S., Clemens, J.C., Hakes, D.J., Barford, D., and Dixon, J. E. (1993) J. Biol. Chem. 268, 17754-17761). Site-directed mutagenesis has now been employed to define amino acid residues in lambda-PPase required for metal ion binding and catalysis. Conservative amino acid substitutions at residues Asp20, His22, Asp49, His76, and Glu77 affected lambda-PPase catalysis and metal ion binding, whereas substitutions at residues Arg53 and Arg73 affected catalysis and substrate binding. Each of these residues is invariant in all phosphoprotein phosphatases, suggesting that these residues may play important roles in binding and catalysis in all of the PPases. Computer-assisted sequence alignment further revealed that lambda-PPase residues Asp20, His22, Asp49, His76, Arg53, and Arg73 lie within three larger regions of PPase sequence identity with the consensus sequence (DXH-(approximately 25)-GDXXD-(approximately 25)-GNHD/E). This motif can be found in a wide variety of phosphoesterases unrelated to the PPases and defines structural and catalytic features utilized by a diverse group of enzymes for the hydrolysis of phosphate esters.

Expression, purification, crystallization, and biochemical characterization of a recombinant protein phosphatase

A protein phosphatase (PPase) from the bacteriophage lambda was overexpressed in Escherichia coli. The recombinant enzyme was purified to homogeneity yielding approximately 17 mg of enzyme from a single liter of bacterial culture. Biochemical characterization of the enzyme showed that it required Mn2+ or Ni2+ as an activator. The recombinant enzyme was active toward serine, threonine, and tyrosine phosphoproteins and phosphopeptides. Surprisingly, the bacterial histidyl phosphoprotein, NRII, was also dephosphorylated by the lambda-PPase. The lambda-PPase shares a number of kinetic and structural properties with the eukaryotic Ser/Thr phosphatases, suggesting that the lambda-PPase will serve as a good model for structure-function studies. Crystallization of the recombinant purified lambda-PPase yielded monoclinic crystals. The crystals diffract to 4.0 A when exposed to synchrotron x-ray radiation.

Photoinactivation of the bovine heart mitochondrial F1-ATPase by [14C]dequalinium cross-links phenylalanine-403 or phenylalanine-406 of an alpha subunit to a site or sites contained within residues 440-459 of a beta subunit

Synthesis of [14C]dequalinium, 1,1'-(1,10-[1,10-14C]decanediyl)bis[4-amino-2-methylquinolinium ], is described, which photoinactivates the bovine heart mitochondrial F1-ATPase (MF1). Maximal photoinactivation occurs on incorporation of about 1.5 mol of [14C]dequalinium/mol of MF1. Three radioactive species were resolved when photoinactivated enzyme was submitted to polyacrylamide gel electrophoresis at pH 4.0 in the presence of tetradecyltrimethylammonium bromide, which correspond to the alpha and beta subunits and a cross-linked species with an M(r) of 116,000. Fractionation of a tryptic digest of photoinactivated enzyme by high-performance liquid chromatography led to isolation of a radioactive peptide which contains residues 399-420 of a alpha subunit. Two fragments containing equal amounts of radioactivity were obtained on fractionation of an endoproteinase Asp-N digest of the isolated radioactive tryptic peptide by high-performance liquid chromatography. Amino acid sequence analysis showed that both fragments contained residues 399-408 of the alpha subunit, but one was missing Phe-alpha 403 and the other was lacking Phe-alpha 406. Fractionation of a cyanogen bromide digest of photoinactivated enzyme followed by trypsin digestion of partially purified cyanogen bromide fragments and fractionation of the resulting radioactive tryptic fragments yielded several radioactive species comprised of residues 399-420 of the alpha subunit cross-linked to residues 440-459 of the beta subunit and a radioactive fragment containing residues 399-420 of the alpha subunit. Partial sequence analyses of the cross-linked fragments suggest that Phe-alpha 403 and Phe-alpha 406 participate in cross-links, whereas no information was obtained on the site or sites of cross-linking in the beta subunit fragment.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional sites in F1-ATPases: location and interactions

This review focuses on the location and interaction of three functional sites in F1-ATPases. These are catalytic sites which are located in beta subunits, noncatalytic nucleotide-binding sites which are located at interfaces of alpha and beta subunits and modulate the hydrolytic activity of the enzyme, and a site that binds inhibitory amphipathic cations which is at an interface of alpha and beta subunits. The latter site may participate in transmission of conformational signals between catalytic sites in F1 and the proton-conducting apparatus of F0 in the intact ATP synthases.

Irradiation of the bovine mitochondrial F1-ATPase previously inactivated with 5'-p-fluorosulfonylbenzoyl-8-azido-[3H]adenosine cross-links His-beta 427 to Tyr-beta 345 within the same beta subunit

The bovine heart mitochondrial F1-ATPase (MF1) is inactivated by 5'-p'-fluorosulfonylbenzoyl-8-azidoadenosine (8-N3-FSBA) with an apparent Kd of 0.47 mM at pH 8.0 and 23 degrees C in the absence of light. Irradiation of dark-inactivated enzyme with long-wavelength UV light produced cross-linked dimers and, to a lesser extent, trimers made up of alpha and beta subunits. Two major radioactive peptides were resolved by high-performance liquid chromatography from tryptic digests of MF1 which had been inactivated with 8-N3-FSB[3H]A at pH 8.0 in the dark. Sequence analysis revealed that one contained Tyr-beta 368 and the other contained His-beta 427 which were labeled in the ratio of 18:15. Sequence analysis of radioactive tryptic peptides isolated from digests of irradiated MF1 derivatized with 8-N3-FSB[3H]A showed that photolysis induced cross-linking of His-427 to Tyr-345 within the same beta subunit in high yield. When MF1 derivatized with 8-N3-FSB[3H]A was irradiated in the presence of beta-mercaptoethanol, alpha-beta cross-links were eliminated, whereas those between His-beta 427 and Tyr-beta 345 were unaffected. Analysis of radioactive peptides in tryptic digests of MF1 derivatized with 8-N3-FSB[3H]A and then irradiated in the presence or absence of beta-mercaptoethanol showed that the nitrene generated from reagent attached to Tyr-beta 368 participates in formation of alpha-beta cross-links in the absence of beta-mercaptoethanol. Therefore, the nitrene generated from reagent tethered to His-beta 427 is shielded from solvent and reacts with the side chain of Tyr-beta 345. In contrast, the nitrene generated from reagent attached to Tyr-beta 368 is exposed to solvent, but in the absence of scavengers reacts with side chains present in the alpha subunit. Irradiation of MF1, partially inactivated with 8-N3-FSBA, led to loss of residual ATPase activity without affecting residual ITPase activity. The amount of photoinactivation was greater when partial dark inactivation was performed at pH 6.9, where modification of His-beta 427 predominates, than when performed at pH 8.0, where modification of Tyr-beta 368 predominates. This suggests that cross-linking of His-beta 427 to Tyr-beta 345, and not cross-linking of alpha and beta subunits, is responsible for the augmented inactivation induced by irradiation.

Inhibition and photoinactivation of the bovine heart mitochondrial F1-ATPase by the cytotoxic agent, dequalinium

The bovine heart mitochondrial F1-ATPase is inhibited in the dark by the amphipathic cation, dequalinium, with a I0.5 of about 12 microM at pH 7.5. When illuminated at 350 nm in the presence of 1.7 microM dequalinium, the F1-ATPase is inactivated with a pseudo-first order rate constant of 7.9 X 10(-3) min-1. The apparent Kd of the dequalinium-enzyme complex was estimated to be about 12.5 microM by examining the rate of inactivation of the ATPase with 1.7-16.7 microM dequalinium. ATP, ADP, Pi, and Mg2+, singly or in combination, protected the ATPase against photoinactivation, with Mg2+ plus Pi being the most effective.