ORCID Profile
0000-0001-7512-7223
Current Organisation
Griffith University
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Publisher: Elsevier BV
Date: 06-2019
Publisher: Wiley
Date: 24-04-2018
Publisher: American Chemical Society (ACS)
Date: 23-01-2012
DOI: 10.1021/BI201541W
Abstract: Chloride intracellular channel proteins exist in both a soluble cytosolic form and a membrane-bound form. The mechanism of conversion between the two forms is not properly understood, although one of the contributing factors is believed to be the variation in pH between the cytosol (~7.4) and the membrane (~5.5). We systematically mutated each of the three histidine residues in CLIC1 to an alanine at position 74 and a phenylalanine at positions 185 and 207. We examined the effect of the histidine-mediated pH dependence on the structure and global stability of CLIC1. None of the mutations were found to alter the global structure of the protein. However, the stability of H74A-CLIC1 and H185F-CLIC1, as calculated from the equilibrium unfolding data, is no longer dependent on pH because similar trends are observed at pH 7.0 and 5.5. The crystal structures show that the mutations result in changes in the local hydrogen bond coordination. Because the mutant total free energy change upon unfolding is not different from that of the wild type at pH 7.0, despite the presence of intermediates that are not seen in the wild type, we propose that it may be the stability of the intermediate state rather than the native state that is dependent on pH. On the basis of the lower stability of the intermediate in the H74A and H185F mutants compared to that of the wild type, we conclude that both His74 and His185 are involved in triggering the pH changes to the conformational stability of wild-type CLIC1 via their protonation, which stabilizes the intermediate state.
Publisher: Cambridge University Press
Date: 19-04-2018
Publisher: Elsevier BV
Date: 02-2021
Publisher: MDPI AG
Date: 24-11-2020
Abstract: International governments’ COVID-19 responses must balance human and economic health. Beyond slowing viral transmission, strict lockdowns have severe economic consequences. This work investigated response stringency, quantified by the Oxford COVID-19 Government Response Tracker’s Stringency Index, and examined how restrictive interventions affected infection rates and gross domestic product (GDP) in China and OECD countries. Accounting for response timing, China imposed the most stringent restrictions, while Sweden and Japan were the least stringent. Expected GDP declines range from −8% (Japan) to −15.4% (UK). While greater restrictions generally slowed viral transmission, they failed to reach statistical significance and reduced GDP (p = 0.006). Timing was fundamental: governments who responded to the pandemic faster saw greater reductions in viral transmission (p = 0.013), but worse decreases in GDP (p = 0.044). Thus, response stringency has a greater effect on GDP than infection rates, which are instead affected by the timing of COVID-19 interventions. Attempts to mitigate economic impacts by delaying restrictions or decreasing stringency may buoy GDP in the short term but increase infection rates, the longer-term economic consequences of which are not yet fully understood. As highly restrictive interventions were successful in some but not all countries, decision-makers must consider whether their strategies are appropriate for the country on health and economic grounds.
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7MD00090A
Abstract: This study reports the most active non-sulfonamide mycobacterial CA inhibitor to date.
Publisher: Wiley
Date: 18-11-2016
Publisher: CSIRO Publishing
Date: 2014
DOI: 10.1071/CH14304
Abstract: New interventions against infectious diseases require a detailed knowledge and understanding of pathogen–host interactions and pathogeneses at the molecular level. The combination of the considerable advances in systems biology research with methods to explore the structural biology of molecules is poised to provide new insights into these areas. Importantly, exploring three-dimensional structures of proteins is central to understanding disease processes, and establishing structure–function relationships assists in identification and assessment of new drug and vaccine targets. Frequently, the molecular arsenal deployed by invading pathogens, and in particular parasites, reveals a common theme whereby families of proteins with conserved three-dimensional folds play crucial roles in infectious processes, but in idual members of such families show high levels of specialisation, which is often achieved through grafting particular structural features onto the shared overall fold. Accordingly, the applicability of predictive methodologies based on the primary structure of proteins or genome annotations is limited, particularly when thorough knowledge of molecular-level mechanisms is required. Such instances exemplify the need for experimental three-dimensional structures provided by protein crystallography, which remain an essential component of this area of research. In the present article, we review two ex les of key protein families recently investigated in our laboratories, which could represent intervention targets in the metabolome or secretome of parasites.
Publisher: Springer Science and Business Media LLC
Date: 07-11-2019
DOI: 10.1038/S41598-019-52593-9
Abstract: Protein-based drug discovery strategies have the distinct advantage of providing insights into the molecular mechanisms of chemical effectors. Currently, there are no known trehalose-6-phosphate phosphatase (TPP) inhibitors that possess reasonable inhibition constants and chemical scaffolds amenable to convenient modification. In the present study, we subjected recombinant TPPs to a two-tiered screening approach to evaluate several erse compound groups with respect to their potential as TPP inhibitors. From a total of 5452 compounds tested, N -(phenylthio)phthalimide was identified as an inhibitor of nematode TPPs with apparent K i values of 1.0 μM and 0.56 μM against the enzymes from the zoonotic roundworms Ancylostoma ceylanicum and Toxocara canis , respectively. Using site-directed mutagenesis, we demonstrate that this compound acts as a suicide inhibitor that conjugates a strictly conserved cysteine residue in the vicinity of the active site of nematode TPPs. The anthelmintic properties of N -(phenylthio)phthalimide were assessed in whole nematode assays using larvae of the ascaroids T. canis and T. cati , as well as the barber’s pole worm Haemonchus contortus . The compound was particularly effective against each of the ascaroids with an IC 50 value of 9.3 μM in the survival assay of T. cati larvae, whereas no bioactivity was observed against H. contortus .
Publisher: Springer Science and Business Media LLC
Date: 17-05-2017
DOI: 10.1038/S41598-017-02220-2
Abstract: Owing to the key role of trehalose in pathogenic organisms, there has recently been growing interest in trehalose metabolism for therapeutic purposes. Trehalose-6-phosphate phosphatase (TPP) is a pivotal enzyme in the most prominent biosynthesis pathway (OtsAB). Here, we compare the enzyme characteristics of recombinant TPPs from five important nematode and bacterial pathogens, including three novel members of this protein family. Analysis of the kinetics of trehalose-6-phosphate hydrolysis reveals that all five enzymes display a burst-like kinetic behaviour which is characterised by a decrease of the enzymatic rate after the pre-steady state. The observed super-stoichiometric burst litudes can be explained by multiple global conformational changes in members of this enzyme family during substrate processing. In the search for specific TPP inhibitors, the trapping of the complex conformational transitions in TPPs during the catalytic cycle may present a worthwhile strategy to explore.
Publisher: Springer Science and Business Media LLC
Date: 21-05-2019
Publisher: Wiley
Date: 18-05-2015
DOI: 10.1111/FEBS.13313
Abstract: The mycobacterial enzyme Rv1284 is a member of the β-carbonic anhydrase family that is considered essential for survival of the pathogen. The active site cavity of this dimeric protein is characterized by an exceptionally small volume and harbours a catalytic zinc ion coordinated by two cysteine and one histidine residue side chains. Using the natural products polycarpine and emodin as chemical probes in crystallographic experiments and stopped-flow enzyme assays, we report that the catalytic activity can be reversibly inhibited by oxidation. Oxidative conditions lead to the removal of one of the active site cysteine residues from the coordination sphere of the catalytic metal ion by engagement in a disulfide bond with another cysteine residue close by. The subsequent loss of the metal ion, which is supported by crystallographic analysis, may thus render the protein catalytically inactive. The oxidative inhibition of Rv1284 can be reversed by exposing the protein to reducing conditions. Because the physical size of the chemical probes used in the present study substantially exceeds the active site volume, we hypothesized that these compounds exert their effects from a surface-bound location and identified Tyr120 as a critical residue for oxidative inactivation. These findings link conditions of oxidative stress to pH homeostasis of the pathogen. Because oxidative stress and acidification are defence mechanisms employed by the innate immune system of the host, we suggest that Rv1284 may be a component of the mycobacterial survival strategy. Atomic coordinates and structure factors have been deposited in the Protein Data Bank under accession numbers 4yf4, 4yf5 and 4yf6.
Publisher: Wiley
Date: 10-01-2019
DOI: 10.1002/BMB.21205
Abstract: The Java software jBar consists of a graphical user interface that allows the user to customize and assemble an included script for R. The scripted R pipeline calculates means and standard errors/deviations for replicates of numerical bivariate data and generates presentations in the form of bar graphs. A two-sided Student's t test is carried out against a user-selected reference and p-values are calculated. The user can enter the data conveniently through the built-in spreadsheet and configure the R pipeline in the graphical user interface. The configured R script is written into a file and then executed. Bar graphs can be generated as static PNG, PDF, and SVG files or as interactive HTML widgets. © 2019 International Union of Biochemistry and Molecular Biology, 47(2): 207-210, 2019.
Publisher: Springer Science and Business Media LLC
Date: 11-09-2014
DOI: 10.1007/S11010-014-2207-Z
Abstract: The chloride intracellular channel protein, CLIC1, is synthesised as a soluble monomer that can reversibly bind membranes. Soluble CLIC1 is proposed to respond to the low pH found at a membrane surface by partially unfolding and restructuring into a membrane-competent conformation. This transition is proposed to be controlled by strategically located "pH-sensor" residues that become protonated at acidic pH. In this study, we investigate the role of two conserved glutamate residues, Glu85 in the N-domain and Glu228 in the C-domain, as pH-sensors. E85L and E228L CLIC1 variants were created to reduce pH sensitivity by permanently breaking the bonds these residues form. The structure and stability of each variant was compared to the wild type at both pH 7.0 and pH 5.5. Neither substitution significantly altered the structure but both decreased the conformational stability. Furthermore, E85L CLIC1 formed a urea-induced unfolding intermediate state at both pH 7 and pH 5.5 compared to wild-type and E228L CLIC1 which only formed the intermediate at pH 5.5. We conclude that Glu85 and Glu228 are two of the five pH-sensor residues of CLIC1 and contribute to the pH-response in different ways. Glu228 lowers the stability of the native state at pH 5.5, while Glu85 contributes both to the stability of the native state and to the formation of the intermediate state. By putting these interactions into the context of the three previously described CLIC1 pH-sensor residues, we propose a mechanism for the conversion of CLIC1 from the soluble state to the pre-membrane form.
Publisher: Public Library of Science (PLoS)
Date: 24-02-2023
DOI: 10.1371/JOURNAL.PONE.0279923
Abstract: Bariatric surgery is an effective treatment for type 2 diabetes and morbid obesity. This paper analyses the clinical and patient-reported outcomes of patients treated through the Bariatric Surgery Initiative, a health system collaboration providing bariatric surgery as a state-wide public service in Queensland, Australia. A longitudinal prospective cohort study was undertaken. Eligible patients had type 2 diabetes and morbid obesity (BMI ≥ 35 kg/m 2 ). Following referral by specialist outpatient clinics, 212 patients underwent Roux-en-Y gastric bypass or sleeve gastrectomy. Outcomes were tracked for a follow-up of 12-months and included body weight, BMI, HbA1c, comorbidities, health-related quality of life, eating behaviour, and patient satisfaction. Following surgery, patients’ average body weight decreased by 23.6%. Average HbA1c improved by 24.4% and 48.8% of patients were able to discontinue diabetes-related treatment. The incidence of hypertension, non-alcoholic steatohepatitis, and renal impairment decreased by 37.1%, 66.4%, and 62.3%, respectively. Patients’ emotional eating scores, uncontrolled eating and cognitive restraint improved by 32.5%, 20.7%, and 6.9%, respectively. Quality of life increased by 18.8% and patients’ overall satisfaction with the treatment remained above 97.5% throughout the recovery period. This study confirmed previous work demonstrating the efficacy of publicly funded bariatric surgery in treating obesity, type 2 diabetes and related comorbidities, and improving patients’ quality of life and eating behaviour. Despite the short follow-up period, the results bode well for future weight maintenance in this cohort.
Publisher: Elsevier BV
Date: 06-2016
DOI: 10.1016/J.EJCB.2016.03.004
Abstract: p97 (VCP) is a homo-hexameric triple-A ATPase that exerts a plethora of cellular processes. Heterozygous missense mutations of p97 cause at least five human neurodegenerative disorders. However, the specific molecular consequences of p97 mutations are hitherto widely unknown. Our in silico structural models of human and Dictyostelium p97 showed that the disease-causing human R93C, R155H, and R155C as well as Dictyostelium R154C, E219K, R154C/E219K p97 mutations constitute variations in surface-exposed locations. In-gel ATPase activity measurements of p97 monomers and hexamers revealed significant mutation- and species-specific differences. While all human p97 mutations led to an increase in ATPase activity, no changes could be detected for the Dictyostelium R154C mutant, which is orthologous to human R155C. The E219K mutation led to an almost complete loss of activity, which was partially recuperated in the R154C/E219K double-mutant indicating p97 inter-domain communication. By means of co-immunoprecipitation experiments we identified an UBX-domain containing Dictyostelium protein as a novel p97 interaction partner. We categorized all UBX-domain containing Dictyostelium proteins and named the interaction partner UBXD9. Pull-down assays and surface plasmon resonance analyses of Dictyostelium UBXD9 or the human orthologue TUG/ASPL/UBXD9 demonstrated direct interactions with p97 as well as species-, mutation- and ATP-dependent differences in the binding affinities. Sucrose density gradient assays revealed that both human and Dictyostelium UBXD9 proteins very efficiently disassembled wild-type, but to a lesser extent mutant p97 hexamers into monomers. Our results are consistent with a scenario in which p97 point mutations lead to differences in enzymatic activities and molecular interactions, which in the long-term result in a late-onset and progressive multisystem disease.
Publisher: Mary Ann Liebert Inc
Date: 12-2019
Abstract: Dipeptidyl peptidase-4 (DPP-4) is considered a major drug target for type 2 diabetes mellitus (T2DM). In addition to T2DM, a regulatory role of DPP-4 was also found in cardiovascular diseases. Existing DPP-4 inhibitors have been reported to have several adverse effects. In this study, a computer-aided drug design approach and its use to detect a novel class of inhibitor for DPP-4 are reported. Through structure and pharmacophore-based screening, we identified 13 hit compounds from an ∼4-million-compound library. Physical interactions of these hits with DPP-4 were studied using docking and explicit solvent molecular dynamics (MD) simulations. Later, MMPBSA binding energy was calculated for the ligand rotein simulation trajectories to determine the stability of compounds in the binding cavity. These compounds have a novel scaffold and exhibited a stable binding mode. "Best-in-screen" compounds (or their closest available analogs) were resourced and their inhibition of DPP-4 activity was experimentally validated using an in vitro enzyme activity assay in the presence of 100 and 10 μM compounds. These assays identified a compound with a spirochromanone center with 53% inhibition activity at a 100 μM concentration. A further five spirochromanone compounds were synthesized and examined in silico and in vitro again, one compound showed 53% inhibitory activity action at 100 μM. Overall, this study identified two novel "spirochromanone" compounds that lowered DPP-4 activity by more than ∼50% at 100 μM. This study also showed the impact of fast in silico drug design techniques utilizing virtual screening and MD to identify novel scaffolds to bind and inhibit DPP-4. Spirochromanone motif identified here may be used to design molecules to achieve drug-like inhibitory action against DPP-4.
Publisher: Portland Press Ltd.
Date: 22-12-2017
DOI: 10.1042/ETLS20170106
Abstract: As opposed to organism-based drug screening approaches, protein-based strategies have the distinct advantage of providing insights into the molecular mechanisms of chemical effectors and thus afford a precise targeting. Capitalising on the increasing number of genome and transcriptome datasets, novel targets in pathogens for therapeutic intervention can be identified in a more rational manner when compared with conventional organism-based methodologies. Trehalose-6-phosphate phosphatases (TPPs) are structurally and functionally conserved enzymes of the trehalose biosynthesis pathway which play a critical role for pathogen survival, in particular, in parasites. The absence of these enzymes and trehalose biosynthesis from mammalian hosts has recently given rise to increasing interest in TPPs as novel therapeutic targets for drugs and vaccines. Here, we summarise some key aspects of the current state of research towards novel therapeutics targeting, in particular, nematode TPPs.
Location: Australia
Location: Australia
No related grants have been discovered for Megan Cross.