Serum leptin levels in children and adolescents with spinal muscular atrophy types 2 and 3✰

AIM

It has been reported that in patients with spinal muscular atrophy (SMA), lower levels of motor function are associated with hyperleptinemia. Additionally, hyperleptinemia has been found to be more frequent in underweight SMA patients. Therefore, we aimed to analyze serum leptin levels in patients with SMA.

METHOD

This was a cross-sectional study of pediatric patients (2-19 years old) with SMA types 2 and 3. The investigations included anthropometric measurements, assessment of pubertal status, motor function evaluation using the Hammersmith Functional Motor Scale - Expanded (HFMSE), and serum leptin levels.

RESULTS

In total, 37 patients (22 with type 2 and 15 with type 3 SMA) were included in the study. The male-to-female ratio was 1:1.3 and 62.2% of patients were prepubertal. No statistically significant correlation was found between the HFMSE score and leptin levels, r_s(35) = 0.24, p = 0.15. There was, however, a strong positive relationship between the body mass index (BMI) z-score and leptin levels, r_s(35) = 0.87, p < 0.001.

CONCLUSION

Serum leptin levels do not seem to be a useful marker of disease severity in children and adolescents with types 2 and 3 SMA. As in the general pediatric population, leptin levels are strongly correlated with BMI, which is a surrogate measure of body fat.

PARE0008 MOBILE APPLICATION “MOJRA” FOR MONITORING PATIENTS WITH RHEUMATOID ARTHRITIS

Background:

In Serbia, regular examinations with a rheumatologist are scheduled on average every 3 to 4 months. With this in mind, there is a real possibility that many patient data during this period may not be presented to the doctor during the examination, either because the patient forgets them or because they may focus on other issues and may not highlight key facts

Objectives:

To overcome this problem, the Association of Patients with Rheumatic Diseases of Serbia-ORS in cooperation with an IT firm developed the application “MojRA”, which was presented at the annual rheumatology congress of Serbia held in September 2019. The application “MojRA” is intended for patients suffering from rheumatoid arthritis - RA. The application enables efficient storage and systematization of data, allows doctors to monitor the condition of their patients between two examinations and have a medical history. “MojRA” is available for now from smartphones running the android operating system on the google play store. The privacy of patient information is guaranteed.

Methods:

Patients with RA will be able to record and store information about important moments during treatment in a simple and transparent way. At each subsequent visit they will be able to describe what happened to their illness in the meantime. The application can create different types of reports and views.

At the same time, the doctor can use the app to inform the patient about her/his condition in real time, which will contribute to better and more meaningful communication. All this would improve the quality of health care, preserving work capacity and improving the quality of life.

Results:

In order to simplify biotherapy committee approval procedure for patients of RA, the “Charger” has been developed in association with ORS and URes. The “Charger” will connect data collected by MojRa to the registry of RA patients, making the whole approval procedure more efficient and transparent.

Testing of the second version of this application is underway, meetings are held between the patients using the application and the IT company that created it.

Plans are to expand the app to other types of arthritis in the near future, too, and will soon be completed for devices running Apple operating systems.

Conclusion:

In addition to being of great benefit to patients and doctors, it can in the future be of immeasurable importance for the savings in the overall health care system of the Republic of Serbia.

References:

[1]Mobile Apps for Rheumatoid Arthritis: Opportunities and Challenges, Mollard E, Michaud K, Rheum Dis Clin, May 2019, Volume 45, Issue 2, Pages 197–209

[2]Apps for People With Rheumatoid Arthritis to Monitor Their Disease Activity: A Review of Apps for Best Practice and Quality, Rebecca Grainger, Hutt Hospital, JMIR Publications, Advancing Digital Health Research, Feb 27, 2017.

[3]ACR Mobile Apps,https://www.rheumatology.org/Learning-Center/Apps,American College of Reumatology.

Disclosure of Interests:

None declared

Assessing and visualising hazard impacts to enhance the resilience of Critical Infrastructures to urban flooding

The design, construction and maintenance of Critical Infrastructures (CI) is commonly based on standards that are rigorous, so as to withstand any climate or weather-linked pressures. However, due to climate change, climate characteristics may shift, resulting in increased frequency/magnitude of potential failures, or exposure to new unknown risks. As vital components for the normal functioning of modern societies, the resilience of CIs under climate stressors encompasses their structural integrity, their operational elements, and their capacity to maximize business output. In this work, we propose an integrated and participatory methodological approach to enhance the resilience of interconnected CIs to urban flooding under climate change, by assessing the risk and introducing adaptation measures. The main objectives of the proposed methodology and approach are: (i) to provide scientific evidence for better understanding of how future climate regimes might affect normal operation of interconnected CI in urban areas during their lifespan; (ii) to assess the cost-effectiveness of different adaptation measures; (iii) to involve local stakeholders and operators in the co-design of the approach, as well as the assessment and the evaluation of adaptation measures; (iv) to combine computational modelling with advanced 3D visualisation techniques for effectively engaging stakeholders in decision making; (v) to include risk assessment and damage functions co-designed by end-users and local stakeholders; (vi) to integrate all of the aforementioned components in a specifically designed cloud platform as a Decision Support System for end-users, (vii) to validate the DSS by the end users and local stakeholders. The paper presents the computational background and tools. Additionally, it describes a Case Study in Torbay, UK, where the full methodology and the proposed participatory approach have been applied, with all the specifics, i.e., the scenarios of extreme flooding, the numerical and visualisation results, the response of the stakeholders and the evaluation of selected adaptation measures.

Marrubium vulgare ethanolic extract induces proliferation block, apoptosis, and cytoprotective autophagy in cancer cells in vitro

Marrubium vulgare is a European medicinal plant with numerous beneficial effects on human health. The aim of the study was to isolate the plant ethanolic extract (MVE) and to investigate its anti-melanoma and anti-glioma effects. MVE was prepared by the modified pharmacopoeial percolation method and characterized by UHPLC-LTQ OrbiTrap MS. MVE dose-dependently reduced viability of melanoma (B16) and glioma (U251) cells, but not peripheral blood mononuclear cells. It arrested cell cycle in S+G2/M phase, which was associated with the activation of MAP kinase p38 and up-regulation of antiproliferative genes p53, p21 and p27. MVE induced oxidative stress, while antioxidants abrogated its antitumor effect. Furthermore, MVE induced mitochondrial depolarization, activation of caspase-9 and -3, Parp cleavage, phosphatidylserine exposure and DNA fragmentation. The mitochondrial apoptotic pathway was associated with the up-regulation of proapoptotic genes Pten, Bak1, Apaf1, and Puma and down-regulation of antiapoptotic genes survivin and Xiap. MVE also stimulated the expression of autophagy-related genes Atg5, Atg7, Atg12, Beclin-1, Gabarab and Sqstm1, as well as LC3-I conversion to the autophagosome associated LC3-II, while autophagy inhibitors exacerbated its cytotoxicity. Finally, the most abundant phenolic components of MVE, ferulic, p-hydroxybenzoic, caffeic and chlorogenic acids, did not exert a profound effect on viability of tumor cells, suggesting that other components individually or in concert are the mediators of the extracts' cytotoxicity. By demonstrating the ability of MVE to inhibit proliferation, induce apoptosis and cytoprotective autophagy, our results suggest that MVE, alone or combined with autophagy inhibitors, could be a good candidate for anti-melanoma and anti-glioma therapy.

Thermal and ultrasonic influence in the formation of nanometer scale hydroxyapatite bio-ceramic

Hydroxyapatite (HAP) is a widely used biocompatible ceramic in many biomedical applications and devices. Currently nanometer-scale forms of HAP are being intensely investigated due to their close similarity to the inorganic mineral component of the natural bone matrix. In this study nano-HAP was prepared via a wet precipitation method using Ca(NO₃)₂ and KH₂PO₄ as the main reactants and NH₄OH as the precipitator under ultrasonic irradiation. The Ca/P ratio was set at 1.67 and the pH was maintained at 9 during the synthesis process. The influence of the thermal treatment was investigated by using two thermal treatment processes to produce ultrafine nano-HAP powders. In the first heat treatment, a conventional radiant tube furnace was used to produce nano-particles with an average size of approximately 30 nm in diameter, while the second thermal treatment used a microwave-based technique to produce particles with an average diameter of 36 nm. The crystalline structure and morphology of all nanoparticle powders produced were investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR). Both thermal techniques effectively produced ultrafine powders with similar crystalline structure, morphology and particle sizes.

Liquid chromatographic-mass spectrometric method for the determination of fluoxetine and norfluoxetine in human plasma: application to clinical study

A selective, sensitive, simple, and rapid method for the simultaneous determination of fluoxetine (FL) and norfluoxetine (nor-FL) was developed and validated, and further applied to analyze plasma samples obtained from FL-treated patients with Parkinson disease (n = 18). After one step liquid-liquid extraction with ethyl acetate, plasma samples were chromatographed on a C8 column. The mobile phase was acetate buffer and acetonitrile (40:60 v/v). Determination of FL and nor-FL was performed with MS detection in selective ion monitoring (SIM) mode, so the other components did not interfere with this assay. FL, nor-FL and flumazenil as internal standard were eluted in 6 min. Recoveries ranged from 89.7 to 96.6% and from 80.2 to 85.3% for FL and nor-FL, respectively. The limit of quantitation under described conditions was 2.5 microg/l for FL and 10 microg/l for nor-FL. The method was found to be reproducible with coefficient of variation less than 9%. The parameters of the method were found to be acceptable to enable its routine use for clinical studies. The method was employed to analyze the Parkinsonian patients' plasma samples. A great deviation in plasma concentrations of FL and nor-FL found among 18 studied patients indicates high pharmacokinetic variability of the drug. Obtained results also indicate absence of the influence of Parkinson disease on the drug disposition.

Plasma albumin level as an indicator of severity of preeclampsia

We propose that hypoalbuminemia in preeclampsia is the result of reduced hepatic blood flow which is secondary to hypovolemia created by higher filtration pressure in the capillaries. Thus, hypoalbuminemia can be identified as an early sign in developing preeclampsia. We reviewed the medical records of 60 patients, aged 22-28, admitted with a diagnosis of preeclampsia during the third trimester of pregnancy. Normotensive patients served as a control group. Albumin levels were correlated with severity of the disorder. Levels between 3.0-3.5 g/dl were seen in both groups. All patients with severe preeclampsia had values below 3.0 gm/dl. Serum albumin levels may serve as an indicator of the severity of preeclampsia.

The separation of hypericine and pseudohypericine from Hypericum perforatum L

The extraction of Hypericum perforatum L. was carried out by the method of ultrasonic maceration. The separation of H. perforatum L. extract in order to obtain hypericine and pseudohypericine rich fractions was carried out by the following chromatographic methods: flash column chromatography, high speed countercurrent chromatography, XAD solid phase extraction and Sephadex column chromatography. The separation by the Sephadex column chromatography gave the best results. Preparative HPLC was used to isolate hypericine and pseudohypericine from fraction 4 obtained by the Sephadex column chromatography procedure.

The Serbian version of the Childhood Health Assessment Questionnaire (CHAQ) and the Child Health Questionnaire (CHQ)

We report herein the results of the cross-cultural adaptation and validation into the Serbian language of the parentís version of two health related quality of life instruments. The Childhood Health Assessment Questionnaire (CHAQ) is a disease specific health instrument that measures functional ability in daily living activities in children with juvenile idiopathic arthritis (JIA). The Child Health Questionnaire (CHQ) is a generic health instrument designed to capture the physical and psychosocial well-being of children independently from the underlying disease. The Serbian CHAQ-CHQ were fully validated with 3 forward and 1 backward translations. A total of 139 subjects were enrolled: 79 patients with JIA (30% systemic onset, 28% polyarticular onset, 6% extended oligoarticular subtype, and 36% persistent oligoarticular subtype) and 60 healthy children. The CHAQ clinically discriminated between healthy subjects and JIA patients, with the systemic, polyarticular and extended oligoarticular subtypes having a higher degree of disability, pain, and a lower overall well-being when compared to their healthy peers. Also the CHQ clinically discriminated between healthy subjects and JIA patients, with the systemic onset, polyarticular onset and extended oligoarticular subtypes having a lower physical and psychosocial well-being when compared to their healthy peers. In conclusion the Serbian version of the CHAQ-CHQ is a reliable, and valid tool for the functional, physical and psychosocial assessment of children with JIA.

Mastitis, polyarthritis and abortion caused by Mycoplasma species bovine group 7 in dairy cattle

OBJECTIVE

To report an outbreak of mastitis, polyarthritis and abortion caused by Mycoplasma sp bovine group 7 in three large, centrally-managed dairies and to review the relevant literature.

DESIGN

Epidemiological, clinical and laboratory data were analysed, collated and reported. Multidisciplinary procedures were employed. These included clinical assessment and comprehensive laboratory investigations of affected calves, aborted foetuses and milk samples. Mycoplasma cultures and genetic analyses of isolates were undertaken to identify the aetiological agent.

RESULTS

About 30% of 240 calves usually kept in a calf rearing facility developed severe polyarthritis as a result of Mycoplasma sp bovine group 7 infection between 2 and 3 weeks of age. Multiple abortions occurred on these farms. Mycoplasma sp bovine group 7 was recovered from the fibrinopurulent synovial exudates of four 14-day-old calves, from the stomach contents and lungs of two aborted foetuses, from 14 of 21 bulk milk and four of 10 mastitic quarters. Three bulk colostrum samples cultured during the outbreak were negative for mycoplasma.

CONCLUSION

Mycoplasma sp bovine group 7 caused significant economic losses as a result of polyarthritis, abortion and mastitis. The disease probably originated from udder infections with spread being facilitated by the decreased use of tetracycline in the treatment of mastitis. Neonatal calves were most likely infected by the consumption of milk contaminated with the organism. Abortions presumably resulted from mycoplasmaemia. This appears to be the first report in Australia of bovine abortion resulting from Mycoplasma sp infection.

The crystal structure of yeast phenylalanine tRNA at 2.0 A resolution: cleavage by Mg(2+) in 15-year old crystals

We have re-determined the crystal structure of yeast tRNA(Phe) to 2. 0 A resolution using 15 year old crystals. The accuracy of the new structure, due both to higher resolution data and formerly unavailable refinement methods, consolidates the previous structural information, but also reveals novel details. In particular, the water structure around the tightly bound Mg(2+) is now clearly resolved, and hence provides more accurate information on the geometry of the magnesium-binding sites and the role of water molecules in coordinating the metal ions to the tRNA. We have assigned a total of ten magnesium ions and identified a partly conserved geometry for high-affinity Mg(2+ )binding. In the electron density map there is also clear density for a spermine molecule binding in the major groove of the TPsiC arm and also contacting a symmetry-related tRNA molecule. Interestingly, we have also found that two specific regions of the tRNA in the crystals are partially cleaved. The sites of hydrolysis are within the D and anticodon loops in the vicinity of Mg(2+).

Immunoblot assays using recombinant antigens for the detection of Mycoplasma hyopneumoniae antibodies

The 36kDa L-lactate dehydrogenase (LDH) and a 29kDa partial fragment of an ABC transporter ATP-binding protein analogue/multidrug resistance protein homologue (PR2) of Mycoplasma hyopneumoniae were tested for their potential as diagnostic antigens. Recombinant LDH was genetically engineered to contain six histidine residues at its C-terminal end, expressed in Escherichia coli and purified to a high degree using Ni(2+)-chelate affinity chromatography. A partial 262 amino acid segment representing the C-terminal end of the PR2 protein was cloned as a glutathione S-transferase (GST) fusion protein, expressed in E. coli and purified by urea extraction. Purified recombinant LDH-6xHis and PR2-GST were then reacted with pig sera in immunoblot assays. Our immunoblots showed that both proteins detected anti-M. hyopneumoniae antibodies in field and experimentally infected pig sera but not in any of the SPF control sera. The two proteins were specific for M. hyopneumoniae as they did not react with sera of pigs infected with the closely related Mycoplasma flocculare and Mycoplasma hyorhinis which are frequently isolated in pigs but are not of particular concern.

Structural analysis of bacterial chemotaxis proteins: components of a dynamic signaling system

Most motile bacteria are capable of directing their movement in response to chemical gradients, a behavior known as chemotaxis. The signal transduction system that mediates chemotaxis in enteric bacteria consists of a set of six cytoplasmic proteins that couple stimuli sensed by a family of transmembrane receptors to behavioral responses generated by the flagellar motors. Signal transduction occurs via a phosphotransfer pathway involving a histidine protein kinase, CheA, and a response regulator protein, CheY, that in its phosphorylated state, modulates the direction of flagellar rotation. Two auxiliary proteins, CheW and CheZ, and two receptor modification enzymes, methylesterase CheB and methyltransferase CheR, influence the flux of phosphoryl groups within this central pathway. This paper focuses on structural characteristics of the four signaling proteins (CheA, CheY, CheB, and CheR) for which NMR or x-ray crystal structures have been determined. The proteins are examined with respect to their signaling activities that involve reversible protein modifications and transient assembly of macromolecular complexes. A variety of data suggest conformational flexibility of these proteins, a feature consistent with their multiple roles in a dynamic signaling pathway.

Chemotaxis receptor recognition by protein methyltransferase CheR

Signal transduction processes commonly involve reversible covalent modifications of receptors. Bacterial chemotaxis receptors are reversibly methylated at specific glutamate residues within coiled-coil regions of their cytoplasmic domains. Methylation is catalyzed by an S-adenosylmethionine-dependent protein methyltransferase, CheR, that binds to a specific sequence at the C-termini of some chemotaxis receptors. From this tethering point, CheR methylates neighboring receptor molecules. We report the crystal structure, determined to 2.2 A resolution, of a complex of the Salmonella typhimurium methyltransferase CheR bound to the methylation reaction product, S-adenosylhomocysteine (AdoHcy), and the C-terminal pentapeptide of the aspartate receptor, Tar. The structure indicates the basis for the specificity of interaction between the chemoreceptors and CheR and identifies a specific receptor binding motif incorporated in the CheR methyltransferase domain.

Structural basis for methylesterase CheB regulation by a phosphorylation-activated domain

We report the x-ray crystal structure of the methylesterase CheB, a phosphorylation-activated response regulator involved in reversible modification of bacterial chemotaxis receptors. Methylesterase CheB and methyltransferase CheR modulate signaling output of the chemotaxis receptors by controlling the level of receptor methylation. The structure of CheB, which consists of an N-terminal regulatory domain and a C-terminal catalytic domain joined by a linker, was solved by molecular replacement methods using independent search models for the two domains. In unphosphorylated CheB, the N-terminal domain packs against the active site of the C-terminal domain and thus inhibits methylesterase activity by directly restricting access to the active site. We propose that phosphorylation of CheB induces a conformational change in the regulatory domain that disrupts the domain interface, resulting in a repositioning of the domains and allowing access to the active site. Structural similarity between the two companion receptor modification enzymes, CheB and CheR, suggests an evolutionary and/or functional relationship. Specifically, the phosphorylated N-terminal domain of CheB may facilitate interaction with the receptors, similar to the postulated role of the N-terminal domain of CheR. Examination of surfaces in the N-terminal regulatory domain of CheB suggests that despite a common fold throughout the response regulator family, surfaces used for protein-protein interactions differ significantly. Comparison between CheB and other response regulators indicates that analogous surfaces are used for different functions and conversely, similar functions are mediated by different molecular surfaces.

Crystal structure of the chemotaxis receptor methyltransferase CheR suggests a conserved structural motif for binding S-adenosylmethionine

BACKGROUND

Flagellated bacteria swim towards favorable chemicals and away from deleterious ones. The sensing of chemoeffector gradients involves chemotaxis receptors, transmembrane proteins that detect stimuli through their periplasmic domains and transduce signals via their cytoplasmic domains to the downstream signaling components. Signaling outputs from chemotaxis receptors are influenced both by the binding of the chemoeffector ligand to the periplasmic domain and by methylation of specific glutamate residues on the cytoplasmic domain of the receptor. Methylation is catalyzed by CheR, an S-adenosylmethionine-dependent methyltransferase. CheR forms a tight complex with the receptor by binding a region of the receptors that is distinct from the methylation site. CheR belongs to a broad class of enzymes involved in the methylation of a variety of substrates. Until now, no structure from the class of protein methyltransferases has been characterized.

RESULTS

The structure of the Salmonella typhimurium chemotaxis receptor methyltransferase CheR bound to S-adenosylhomocysteine, a product and inhibitor of the methylation reaction, has been determined at 2.0 A resolution. The structure reveals CheR to be a two-domain protein, with a smaller N-terminal helical domain linked through a single polypeptide connection to a larger C-terminal alpha/beta domain. The C-terminal domain has the characteristics of a nucleotide-binding fold, with an insertion of a small antiparallel beta sheet subdomain. The S-adenosylhomocysteine-binding site is formed mainly by the large domain, with contributions from residues within the N-terminal domain and the linker region.

CONCLUSIONS

The CheR structure shares some structural similarities with small molecule DNA and RNA methyltransferases, despite a lack of sequence similarity among them. In particular, there is significant structural preservation of the S-adenosylmethionine-binding clefts; the specific length and conformation of a loop in the alpha/beta domain seems to be required for S-adenosylmethionine binding within these enzymes. Unique structural features of CheR, such as the beta subdomain, are probably necessary for CheR's specific interaction with its substrates, the bacterial chemotaxis receptors.

Manipulating systemic and mucosal immune responses with skin-deliverable adjuvants

Most medically important bacterial and viral pathogens gain entry into the body either via the skin or a mucosal surface. Vaccination provides a viable and cost-effective strategy for the prevention of such diseases and it has always been a principal aim with vaccinologists, to be able to promote simultaneously, protective immune responses both systemically and at mucosal surfaces. The paradigm that mucosal immunity is best stimulated by exposure to antigen via a mucosal route simply because inductive sites such as Peyer's patches and bronchial associated lymphoid tissues are located in the mucosal epithelium, has promoted a plethora of immunizing strategies aimed at delivering both antigen and adjuvant to mucosal surfaces. We have developed a novel adjuvant system capable of intradermal delivery of antigens complexed in an ISCOSOME delivery vehicle. This adjuvant, referred to as a skin and mucosal adjuvant or SAMA4, was efficacious in eliciting both systemic and mucosal IgG and IgA antibodies in sheep, pigs and mice. SAMA4 does not induce granulomatous lesions at the site of vaccine delivery and can be used to deliver adjuvanted antigens by other routes including intranasal, oral and intravaginal. Using ovalbumin as a test antigen, intradermally delivered ovalbumin-SAMA4 complexes was found to be very effective in promoting a cytotoxic T cell response. Attempts to dissect the mode of action of SAMA4 by flow cytometric analysis of lymphocyte populations from the spleen, lung, liver and thymus revealed an effect of route of vaccine delivery upon the composition of specific lymphocyte subsets in these various organ compartments. From this, it can be inferred that SAMA4 induced a route-dependent re-mobilization and alteration in lymphocyte trafficking patterns. Other mucosal adjuvants such as cholera toxin B and microspheres, when injected intradermally, tended to promote primarily, an IgG and not an IgA response against hte carrier antigen.

Crystallization and preliminary x-ray studies of NADPH-cytochrome P450 reductase

NADPH-cytochrome P450 reductase (CPR; NADPH:ferrihemoprotein reductase, EC 1.6.2.4) catalyzes the transfer of electrons to all known microsomal cytochromes P450. CPR is unique in that it is one of only two mammalian enzymes known to contain both flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN), the other being the various isoforms of nitric oxide synthase. Similarities in amino acid sequence and in functional domain arrangement with other key flavoproteins, including nitric oxide synthase, make CPR an excellent prototype for studies of interactions between two flavin cofactors. We have obtained diffraction-quality crystals of rat liver CPR, expressed in Escherichia coli and solubilized by limited proteolysis with trypsin. The crystals were grown in Hepes buffer (pH 7.0), containing polyethylene glycol 4500 and NaCl. The crystals belong to the orthorhombic space group P2(1)2(1)2(1), with unit cell dimensions a = 103.3 A, b = 116.1 A, and c = 120.4 A. If we assume that there are two molecules of the 72-kDa CPR polypeptide per asymmetric unit, the calculated value of Vm is 2.54 A3/Da.

Purification, crystallization, and preliminary X-ray diffraction analyses of the bacterial chemotaxis receptor modifying enzymes

Bacterial chemotaxis receptor modifying enzymes from Salmonella typhimurium have been crystallized using microseeding techniques. The crystals of the S-adenosyl-L-methionine-dependent methyltransferase, CheR, belong to the monoclinic space group P21 with cell constants a = 55.1 A, b = 48.1 A, c = 63.1 A, beta = 112.3 degrees. The crystals of the catalytic domain of the methylesterase, CheB, belong to the trigonal space group P3(2)21 or P3(1)21 with unit cell dimensions of a = b = 63.4 A, c = 86.8 A. Both crystals contain one molecule per asymmetric unit and have calculated Matthews' volumes of 2.4 A3/Da.

Three-dimensional structure of butyryl-CoA dehydrogenase from Megasphaera elsdenii

The crystal structure of butyryl-CoA dehydrogenase (BCAD) from Megasphaera elsdenii complexed with acetoacetyl-CoA has been solved at 2.5 A resolution. The enzyme crystallizes in the P422 space group with cell dimensions a = b = 107.76 A and c = 153.67 A. BCAD is a bacterial analog of short chain acyl-CoA dehydrogenase from mammalian mitochondria. Mammalian acyl-CoA dehydrogenases are flavin adenine dinucleotide (FAD)-containing enzymes that catalyze the first step in the beta-oxidation of fatty acids. Although specific for substrate chain lengths, they exhibit high sequence homology. The structure of BCAD was solved by the molecular replacement method using the atomic coordinates of pig liver medium chain acyl-CoA dehydrogenase (MCAD). The structure was refined to an R-factor of 19.3%. The overall polypeptide fold of BCAD is similar to that of MCAD. E367 in BCAD is at the same position and in a similar conformation as the catalytic base in MCAD, E376. The main enzymatic differences between BCAD and MCAD are their substrate specificities and the significant oxygen reactivity exhibited by BCAD but not by MCAD. The substrate binding cavity of BCAD is relatively shallow compared to that of MCAD, as consequences of both a single amino acid insertion and differences in the side chains of the helices that make the binding site. The si-face of the FAD in BCAD is more exposed to solvent than that in MCAD. Therefore solvation can stabilize the superoxide anion and considerably increase the rate of oxidation of reduced flavin in the bacterial enzyme.

Identification of the catalytic base in long chain acyl-CoA dehydrogenase

We have used molecular modeling and site-directed mutagenesis to identify the catalytic residues of human long chain acyl-CoA dehydrogenase. Among the acyl-CoA dehydrogenases, a family of flavoenzymes involved in beta-oxidation of fatty acids, only the three-dimensional structure of the medium chain fatty acid specific enzyme from pig liver has been determined (Kim, J.-J.P., Wang, M., & Paschke, R. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 7523-7527). Despite the overall sequence homology, the catalytic residue (E376) of medium chain acyl-CoA dehydrogenase is not conserved in isovaleryl- and long chain acyl-CoA dehydrogenases. A molecular model of human long chain acyl-CoA dehydrogenase was derived using atomic coordinates determined by X-ray diffraction studies of the pig medium chain specific enzyme, interactive graphics, and molecular mechanics calculations. The model suggests that E261 functions as the catalytic base in the long-chain dehydrogenase. An altered dehydrogenase in which E261 was replaced by a glutamine was constructed, expressed, purified, and characterized. The mutant enzyme exhibited less than 0.02% of the wild-type activity. These data strongly suggest that E261 is the base that abstracts the alpha-proton of the acyl-CoA substrate in the catalytic pathway of this dehydrogenase.

Restriction-endonuclease analysis of Australian isolates of Leptospira interrogans serovar hardjo from cattle with agalactia and abortion

Polyacrylamide gel electrophoresis and agarose gel electrophoresis were used to resolve restriction endonuclease digests of 20 Australian Isolates of Leptospira interrogans cultured from urine samples of cattle with agalactia and abortion. The restriction endonuclease profiles of 19 isolates closely matched the profiles of L interrogans serovar hardjo subtype hardjobovis reference strains. The remaining isolate had a different restriction profile from subtype hardjobovis and subtype hardjoprajitno reference strains and was serologically identified as serovar pomona. Silver staining of polyacrylamide gels gave enhanced resolution of restriction fragments compared with the traditional method of ethidium bromide staining of agarose gels.