Life Sciences Commons^™

Design, Assessment, And In Vivo Evaluation Of A Computational Model Illustrating The Role Of Cav1 In Cd4+ T-Lymphocytes, Brittany D. Conroy, Tyler A. Herek, Timonthy D. Shew, Matthew Latner, Joshua J. Larson, Laura Allen, Paul H. Davis, Tomáš Helikar, Christine E. Cutucache

Department of Biochemistry: Faculty Publications

Caveolin-1 (CAV1) is a vital scaffold protein heterogeneously expressed in both healthy and malignant tissue. We focus on the role of CAV1 when overexpressed in T-cell leukemia. Previously, we have shown that CAV1 is involved in cell-to-cell communication, cellular proliferation, and immune synapse formation; however, the molecular mechanisms have not been elucidated.We hypothesize that the role of CAV1 in immune synapse formation contributes to immune regulation during leukemic progression, thereby warranting studies of the role of CAV1 in CD4⁺ T-cells in relation to antigen-presenting cells. To address this need, we developed a computational model of a CD4⁺ immune …

Overexpression Of Patatin-Related Phospholipase Aiiiβ Altered The Content And Composition Of Sphingolipids In Arabidopsis, Maoyin Li, Jennifer E. Markham, Xuemin Wang

Department of Biochemistry: Faculty Publications

In plants, fatty acids are primarily synthesized in plastids and then transported to the endoplasmic reticulum (ER) for synthesis of most of the complex membrane lipids, including glycerolipids and sphingolipids. The first step of sphingolipid synthesis, which uses a fatty acid and a serine as substrates, is critical for sphingolipid homeostasis; its disruption leads to an altered plant growth. Phospholipase As have been implicated in the trafficking of fatty acids from plastids to the ER. Previously, we found that overexpression of a patatin-related phospholipase, pPLAIIIβ, resulted in a smaller plant size and altered anisotropic cell expansion. Here, we determined the …

Sensitivity Analysis Of Biological Boolean Networks Using Information Fusion Based On Nonadditive Set Functions, Naomi Kochi, Tomáš Helikar, Laura Allen, Jim A. Rogers, Zhenyuan Wang, Mihaela T. Matache

Department of Biochemistry: Faculty Publications

Background: An algebraic method for information fusion based on nonadditive set functions is used to assess the joint contribution of Boolean network attributes to the sensitivity of the network to individual node mutations. The node attributes or characteristics under consideration are: in-degree, out-degree, minimum and average path lengths, bias, average sensitivity of Boolean functions, and canalizing degrees. The impact of node mutations is assessed using as target measure the average Hamming distance between a non-mutated/wild-type network and a mutated network.

Results: We find that for a biochemical signal transduction network consisting of several main signaling pathways whose nodes …

Use Of Cysteine-Reactive Crosslinkers To Probe Conformational Flexibility Of Human Dj-1 Demonstrates That Glu18 Mutations Are Dimers, Janani Prahlad, David N. Hauser, Nicole M. Milkovic, Mark R. Cookson, Mark A. Wilson

Department of Biochemistry: Faculty Publications

The oxidation of a key cysteine residue (Cys106) in the parkinsonism-associated protein DJ-1 regulates its ability to protect against oxidative stress and mitochondrial damage. Cys106 interacts with a neighboring protonated Glu18 residue, stabilizing the Cys106-SO₂ ⁻ (sulfinic acid) form of DJ-1. To study this important post-translational modification, we previously designed several Glu18 mutations (E18N, E18D, E18Q) that alter the oxidative propensity of Cys106. However, recent results suggest these Glu18 mutations cause loss of DJ-1 dimerization, which would severely compromise the protein’s function. The purpose of this study was to conclusively determine the oligomerization state of these mutants using X-ray …

The Evolution Of Respiratory O2/No Reductases: An Out-Of-The-Phylogenetic-Box Perspective, Anne-Lise Ducluzeau, Barbara Schoepp-Cothenet, Robert Van Lis, Frauke Baymann, Michael J. Russell, Wilfgang Nitschke

Department of Biochemistry: Faculty Publications

Complex life on our planet crucially depends on strong redox disequilibria afforded by the almost ubiquitous presence of highly oxidizing molecular oxygen. However, the history of O₂-levels in the atmosphere is complex and prior to the Great Oxidation Event some 2.3 billion years ago, the amount of O₂ in the biosphere is considered to have been extremely low as compared with present-day values. Therefore the evolutionary histories of life and of O₂-levels are likely intricately intertwined. The obvious biological proxy for inferring the impact of changing O₂-levels on life is the evolutionary history …

A Course-Based Research Experience: How Benefits Change With Increased Investment In Instructional Time, Christopher D. Shaffer, Cheryl Bailey, Students And Tas In Genomics Education Partnership Courses

Department of Biochemistry: Faculty Publications

There is widespread agreement that science, technology, engineering, and mathematics programs should provide undergraduates with research experience. Practical issues and limited resources, however, make this a challenge.We have developed a bioinformatics project that provides a coursebased research experience for students at a diverse group of schools and offers the opportunity to tailor this experience to local curriculum and institution-specific student needs. We assessed both attitude and knowledge gains, looking for insights into how students respond given this wide range of curricular and institutional variables. While different approaches all appear to result in learning gains, we find that a significant investment …

Structures Of The Puta Peripheral Membrane Flavoenzyme Reveal A Dynamic Substrate-Channeling Tunnel And The Quinone-Binding Site, Harkewal Singh, Benjamin W. Arentson, Donald F. Becker, John J. Tanner

Department of Biochemistry: Faculty Publications

Proline utilization A (PutA) proteins are bifunctional peripheral membrane flavoenzymes that catalyze the oxidation of L-proline to L-glutamate by the sequential activities of proline dehydrogenase and aldehyde dehydrogenase domains. Located at the inner membrane of Gram-negative bacteria, PutAs play a major role in energy metabolism by coupling the oxidation of proline imported from the environment to the reduction of membrane-associated quinones. Here, we report seven crystal structures of the 1,004- residue PutA from Geobacter sulfurreducens, along with determination of the protein oligomeric state by small-angle X-ray scattering and kinetic characterization of substrate channeling and quinone reduction. The structures reveal …

Genome-Wide Rnai Ionomics Screen Reveals New Genes And Regulation Of Human Trace Element Metabolism, Mikalai I. Malinouski, Nesrin M. Hasan, Yan Zhang, Javier Seravalli, Jie Lin, Andrei Avanesov, Svetlana Lutsenko, Vadim N. Gladyshev

Department of Biochemistry: Faculty Publications

Trace elements are essential for human metabolism and dysregulation of their homoeostasis is associated with numerous disorders. Here we characterize mechanisms that regulate trace elements in human cells by designing and performing a genome-wide high-throughput siRNA/ionomics screen, and examining top hits in cellular and biochemical assays. The screen reveals high stability of the ionomes, especially the zinc ionome, and yields known regulators and novel candidates. We further uncover fundamental differences in the regulation of different trace elements. Specifically, selenium levels are controlled through the selenocysteine machinery and expression of abundant selenoproteins; copper balance is affected by lipid metabolism and requires …

Arabidopsis Accelerated Cell Death 11, Acd11, Is A Ceramide-1-Phosphate Transfer Protein And Intermediary Regulator Of Phytoceramide Levels, Dhirendra K. Simanshu, Xiuhong Zhai, David Munch, Daniel Hofius, Jennifer E. Markham, Jacek Bielawski, Alicja Bielawska, Lucy Malinina, Julian G. Molotkovsky, John W. Mundy, Dinshaw J. Patel, Rhoderick E. Brown

Department of Biochemistry: Faculty Publications

The accelerated cell death 11 (acd11) mutant of Arabidopsis provides a genetic model for studying immune response activation and localized cellular suicide that halt pathogen spread during infection in plants. Here, we elucidate ACD11 structure and function and show that acd11 disruption dramatically alters the in vivo balance of sphingolipid mediators that regulate eukaryotic-programmed cell death. In acd11 mutants, normally low ceramide-1- phosphate (C1P) levels become elevated, but the relatively abundant cell death inducer phytoceramide rises acutely. ACD11 exhibits selective intermembrane transfer of C1P and phyto-C1P. Crystal structures establish C1P binding via a surface-localized, phosphate headgroup recognition center …

Emerging Roles For Hyaluronidase In Cancer Metastasis And Therapy, Caitlin O. Mcatee, Joseph J. Barycki, Melanie A. Simpson

Department of Biochemistry: Faculty Publications

Hyaluronidases are a family of five human enzymes that have been differentially implicated in the progression of many solid tumor types, both clinically and in functional studies. Advances in the past five years have clarified many apparent contradictions, (1) by demonstrating that specific hyaluronidases have alternative substrates to hyaluronan (HA) or do not exhibit any enzymatic activity, (2) that high molecular weight HA polymers elicit signaling effects that are opposite those of the hyaluronidase-digested HA oligomers, and (3) that it is actually the combined overexpression of HA synthesizing enzymes with hyaluronidases that confers tumorigenic potential. This review examines the literature …

Saturated Free Fatty Acids Induce Cholangiocyte Lipoapoptosis, Sathish Kumar Natarajan, Sally A. Ingham, Ashley M. Mohr, Cody J. Wehrkamp, Anuttoma Ray, Sohini Roy, Sophie C. Cazanave, Mary Anne Phillippi, Justin L. Mott

Department of Biochemistry: Faculty Publications

Recent studies have identified a cholestatic variant of nonalcoholic fatty liver disease (NAFLD) with portal inflammation and ductular reaction. Based on reports of biliary damage, as well as increased circulating free fatty acids (FFAs) in NAFLD, we hypothesized the involvement of cholangiocyte lipoapoptosis as a mechanism of cellular injury. Here, we demonstrate that the saturated FFAs palmitate and stearate induced robust and rapid cell death in cholangiocytes. Palmitate and stearate induced cholangiocyte lipoapoptosis in a concentration-dependent manner in multiple cholangiocyte-derived cell lines. The mechanism of lipoapoptosis relied on the activation of caspase 3/7 activity. There was also a significant up-regulation …

Stress-Triggered Activation Of The Metalloprotease Oma1 Involves Its C-Terminal Region And Is Important For Mitochondrial Stress Protection In Yeast, Iryna Bohovych, Garrett Donaldson, Sara Christianson, Nataliya Zahayko, Oleh Khalimonchuk

Department of Biochemistry: Faculty Publications

Background: Oma1 is a conserved membrane-bound protease that forms a high molecular mass complex.

Results: Oma1 activity is induced by stress stimuli and required for survival. The activation is linked to changes in Oma1 oligomer stability and involves its C-terminal region.

Conclusion: Oma1 function is activated by mitochondrial stress and is important for stress tolerance.

Significance: Novel insights into Oma1 function and a potential stress activation mechanism are provided.

Evidence For Hysteretic Substrate Channeling In The Proline Dehydrogenaseand ∆1-Pyrroline-5-Carboxylate Dehydrogenase Coupled Reaction Of Proline Utilizationa(Puta), Michael A Moxley, Nikhilesh Sanyal, Navasona Krishnan, John J. Tanner, Donald F. Becker

Department of Biochemistry: Faculty Publications

Background: PutA from Escherichia coli is a bifunctional enzyme and transcriptional repressor in proline catabolism.

Results: Steady-state and transient kinetic data revealed a mechanism in which the two enzymatic reactions are coupled by an activation step.

Conclusion: Substrate channeling in PutA exhibits hysteretic behavior.

Significance: This is the first kinetic model of bi-enzyme activity in PutA and reveals a novel mechanism of channeling activation.

Preliminary Joint X-Ray And Neutron Protein Crystallographic Studies Of Ecdhfr Complexed With Folate And Nadp+, Qun Wan, Audrey Y. Kovalevsky, Mark A. Wilson, Brad C. Bennett, Paul Langan, Chris Dealwis

Department of Biochemistry: Faculty Publications

A crystal of Escherichia coli dihydrofolate reductase (ecDHFR) complexed with folate and NADP⁺ of 4 x 1.3 x 0.7 mm (3.6 mm³) in size was obtained by sequential application of microseeding and macroseeding. A neutron diffraction data set was collected to 2.0 A resolution using the IMAGINE diffractometer at the High Flux Isotope Reactor within Oak Ridge National Laboratory. A 1.6 A resolution X-ray data set was also collected from a smaller crystal at room temperature. The neutron and X-ray data were used together for joint refinement of the ecDHFR–folate–NADP⁺ ternary-complex structure in order to examine …

Evaluation Of Three Herbicide Resistance Genes For Use In Genetic Transformations And For Potential Crop Protection In Algae Production, Andrew J. Bruggeman, Daniel Kuehler, Donald P. Weeks

Department of Biochemistry: Faculty Publications

Genes conferring resistance to the herbicides glyphosate, oxyfluorfen and norflurazon were developed and tested for use as dominant selectable markers in genetic transformation of Chlamydomonas reinhardtii and as potential tools for the protection of commercial-scale algal production facilities against contamination by organisms sensitive to these broad-spectrum herbicides. A synthetic glyphosate acetyltransferase (GAT) gene, when fitted with a strong Chlamydomonas promoter, conferred a 2.79-fold increase in tolerance to the EPSPS inhibitor, glyphosate, in transgenic cells compared with progenitor WT cells. A mutant Chlamydomonas protoporphyrinogen oxidase (protox, PPO) gene previously shown to produce an enzyme insensitive to PPO-inhibiting herbicides, when genetically engineered, …

Homogeneous Low-Molecular-Weight Heparins With Reversible Anticoagulant Activity, Yongmei Xu, Chao Cai, Kasemsiri Chandarajoti, Po-Hung Hsieh, Lingyun Li, Truong Q. Pham, Erica M. Sparkenbaugh, Juzheng Sheng, Nigel S. Key, Rafal Pawlinski, Edward N. Harris, Robert J. Linhardt, Jian Liu

Department of Biochemistry: Faculty Publications

Low-molecular-weight heparins (LMWHs) are carbohydrate-based anticoagulants clinically used to treat thrombotic disorders, but impurities, structural heterogeneity or functional irreversibility can limit treatment options. We report a series of synthetic LMWHs prepared by cost-effective chemoenzymatic methods. The high activity of one defined synthetic LMWH against human factor Xa (FXa) was reversible in vitro and in vivo using protamine, demonstrating that synthetically accessible constructs can have a critical role in the next generation of LMWHs.

Pharmacokinetic And Biodistribution Assessment Of A Near Infrared-Labeled Psma-Specific Small Molecule In Tumor-Bearing Mice, Joy L. Kovar, Lael L. Cheung, Melanie A. Simpson, D. Michael Olive

Department of Biochemistry: Faculty Publications

Prostate cancer is themost frequently diagnosed cancer in men and often requires surgery. Use of near infrared (NIR) technologies to perform image-guided surgery may improve accurate delineation of tumor margins. To facilitate preclinical testing of such outcomes, here we developed and characterized a PSMA-targeted small molecule, YC-27. IRDye 800CW was conjugated to YC-27 or an anti-PSMA antibody used for reference. Human 22Rv1, PC3M-LN4, and/or LNCaP prostate tumor cells were exposed to the labeled compounds. In vivo targeting and clearance properties were determined in tumor-bearing mice. Organs and tumors were excised and imaged to assess probe localization. YC-27 exhibited a dose …

Stress Adaptation In A Pathogenic Fungus, Alistair J. P. Brown, Susan Budge, Despoina Kaloriti, Anna Tillmann, Mette D. Jacobsen, Zhikang Yin, Iuliana V. Ene, Iryna Bohovych, Doblin Sandai, Stavroula Kastora, Joanna Potrykus, Elizabeth R. Ballou, Delma S. Childers, Shahida Shahana, Michelle D. Leach

Department of Biochemistry: Faculty Publications

Candida albicans is a major fungal pathogen of humans. This yeast is carried by many individuals as a harmless commensal, but when immune defences are perturbed it causes mucosal infections (thrush). Additionally, when the immune system becomes severely compromised, C. albicans often causes life-threatening systemic infections. A battery of virulence factors and fitness attributes promote the pathogenicity of C. albicans. Fitness attributes include robust responses to local environmental stresses, the inactivation of which attenuates virulence. Stress signalling pathways in C. albicans include evolutionarily conserved modules. However, there has been rewiring of some stress regulatory circuitry such that the roles of …

Emerging Regulatory Paradigms In Glutathione Metabolism, Yilin Liu, Annastasia S. Hyde, Melanie A. Simpson, Joseph J. Barycki

Department of Biochemistry: Faculty Publications

One of the hallmarks of cancer is the ability to generate and withstand unusual levels of oxidative stress. In part, this property of tumor cells is conferred by elevation of the cellular redox buffer glutathione. Though enzymes of the glutathione synthesis and salvage pathways have been characterized for several decades, we still lack a comprehensive understanding of their independent and coordinate regulatory mechanisms. Recent studies have further revealed that overall central metabolic pathways are frequently altered in various tumor types, resulting in significant increases in biosynthetic capacity, and feeding into glutathione synthesis. In this review, we will discuss the enzymes …

Mechanisms Underlying The Exquisite Sensitivity Of Candida Albicans To Combinatorial Cationic And Oxidative Stress That Enhances The Potent Fungicidal Activity Of Phagocytes, Despoina Kaloriti, Mette Jacobsen, Zhikang Yin, Miranda Patterson, Anna Tillmann, Deborah A. Smith, Emily Cook, Tao You, Melissa J. Grimm, Iryna Bohovych, Celso Grebogi, Brahm H. Segal, Neil A.R. Gow, Ken Haynes, Janet Quinn, Alistair J.P. Brown

Department of Biochemistry: Faculty Publications

Immune cells exploit reactive oxygen species (ROS) and cationic fluxes to kill microbial pathogens, such as the fungus

Candida albicans. Yet, C. albicans is resistant to these stresses in vitro. Therefore, what accounts for the potent antifungal activity

of neutrophils? We show that simultaneous exposure to oxidative and cationic stresses is much more potent than the individual

stresses themselves and that this combinatorial stress kills C. albicans synergistically in vitro.We also show that the high

fungicidal activity of human neutrophils is dependent on the combinatorial effects of the oxidative burst and cationic fluxes, as

their pharmacological attenuation with …

Oxidative Stress, Redox Signaling, And Autophagy: Cell Death Versus Survival, Juliana Navarro-Yepes, Michaela Burns, Anandhan Annadurai, Oleh Khalimonchuk, Luz Maria Del Razo, Betzabet Quintanilla-Vega, Aglaia Pappa, Mihalis I. Panayiotidis, Rodrigo Franco

Department of Biochemistry: Faculty Publications

Significance: The molecular machinery regulating autophagy has started becoming elucidated, and a number of studies have undertaken the task to determine the role of autophagy in cell fate determination within the context of human disease progression. Oxidative stress and redox signaling are also largely involved in the etiology of human diseases, where both survival and cell death signaling cascades have been reported to be modulated by reactive oxygen species (ROS) and reactive nitrogen species (RNS). Recent Advances: To date, there is a good understanding of the signaling events regulating autophagy, as well as the signaling processes by which alterations in …

Ycf1-Mediated Cadmium Resistance In Yeast Is Dependent On Copper Metabolism And Antioxidant Enzymes, Wenzhong Wei, Nathan Smith, Xiaobin Wu, Heejeong Kim, Javier Seravalli, Oleh Khalimonchuk, Jaekwon Lee

Department of Biochemistry: Faculty Publications

Aims: Acquisition and detoxification of metal ions are vital biological processes. Given the requirement of metallochaperones in cellular copper distribution and metallation of cuproproteins, this study investigates whether the metallochaperones also deliver metal ions for transporters functioning in metal detoxification. Results: Resistance to excess cadmium and copper of the yeast Saccharomyces cerevisiae, which is conferred by PCA1 and CaCRP1 metal efflux P-type ATPases, respectively, does not rely on known metallochaperones, Atx1p, Ccs1p, and Cox17p. Copper deficiency induced by the expression of CaCRP1 encoding a copper exporter occurs in the absence of Atx1p. Intriguingly, CCS1 encoding the copper chaperone for superoxide …

Evidence That The C‑Terminal Domain Of A Type B Puta Protein Contributes To Aldehyde Dehydrogenase Activity And Substrate Channeling, Min Luo, Shelbi Christgen, Nikhilesh Sanyal, Benjamin W. Arentson, Donald F. Becker, John J. Tanner

Department of Biochemistry: Faculty Publications

Proline utilization A (PutA) is a bifunctional enzyme that catalyzes the oxidation of proline to glutamate. Structures of type A PutAs have revealed the catalytic core consisting of proline dehydrogenase (PRODH) and Δ1- pyrroline-5-carboxylate dehydrogenase (P5CDH) modules connected by a substrate-channeling tunnel. Type B PutAs also have a C-terminal domain of unknown function (CTDUF) that is absent in type A PutAs. Small-angle X-ray scattering (SAXS), mutagenesis, and kinetics are used to determine the contributions of this domain to PutA structure and function. The 1127-residue Rhodobacter capsulatus PutA (RcPutA) is used as a representative CTDUF-containing type B PutA. The reaction progress …

Comparative Analyses Of Three Chlorella Species In Response To Light And Sugar Reveal Distinctive Lipid Accumulation Patterns In The Microalga C. Sorokiniana, Julian N. Rosenberg, Naoko Kobayashi, Austin Barnes, Eric A. Noel, Michael J. Betenbaugh, George A. Oyler

Department of Biochemistry: Faculty Publications

While photosynthetic microalgae, such as Chlorella, serve as feedstocks for nutritional oils and biofuels, heterotrophic cultivation can augment growth rates, support high cell densities, and increase triacylglycerol (TAG) lipid content. However, these species differ significantly in their photoautotrophic and heterotrophic characteristics. In this study, the phylogeny of thirty Chlorella strains was determined in order to inform bioprospecting efforts and detailed physiological assessment of three species. The growth kinetics and lipid biochemistry of C. protothecoides UTEX 411, C. vulgaris UTEX 265, and C. sorokiniana UTEX 1230 were quantified during photoautotrophy in Bold’s basal medium (BBM) and heterotrophy in BBM supplemented …

Book Review Of Dane Kennedy, The Last Blank Spaces: Exploring Africa And Australia, Adrian S. Wisnicki

Department of Biochemistry: Faculty Publications

Mid-nineteenth-century British exploration, particularly the stories of the “heroic” individuals who carried out this exploration, remains a topic of worldwide interest, as most recently evidenced by the many events in Britain and Africa celebrating the 2013 bicentenary of David Livingstone’s birth. Dane Kennedy’s intriguing study takes issue with such readings of the historical record by foregrounding an epistemological tension that lies at the heart of nineteenthcentury British exploration discourse and practice. The book examines the collision—as it played out in the exploration of African and Australia—between metropolitan scientific protocols and non-Western quotidian realities. Nineteenth-century explorers, argues Kennedy, left home with …

New Clox Systems For Rapid And Efficient Gene Disruption In Candida Albicans, Shahida Shahana, Delma S. Childers, Elizabeth R. Ballou, Iryna Bohovych, Frank C. Odds, Neil A.R. Gow, Alistair J.P. Brown

Department of Biochemistry: Faculty Publications

Precise genome modification is essential for the molecular dissection of Candida albicans, and is yielding invaluable information about the roles of specific gene functions in this major fungal pathogen of humans. C. albicans is naturally diploid, unable to undergo meiosis, and utilizes a non-canonical genetic code. Hence, specialized tools have had to be developed for gene disruption in C. albicans that permit the deletion of both target alleles, and in some cases, the recycling of the Candida-specific selectable markers. Previously, we developed a tool based on the Cre recombinase, which recycles markers in C. albicans with 90–100% efficiency via …

Xiap Antagonist Embelin Inhibited Proliferation Of Cholangiocarcinoma Cells, Cody J. Wehrkamp, Ashley R. Gutwein, Sathish Kumar Natarajan, Mary Anne Phillippi, Justin L. Mott

Department of Biochemistry: Faculty Publications

Cholangiocarcinoma cells are dependent on antiapoptotic signaling for survival and resistance to death stimuli. Recent mechanistic studies have revealed that increased cellular expression of the E3 ubiquitin-protein ligase X-linked inhibitor of apoptosis (XIAP) impairs TRAIL- and chemotherapy-induced cytotoxicity, promoting survival of cholangiocarcinoma cells. This study was undertaken to determine if pharmacologic antagonism of XIAP protein was sufficient to sensitize cholangiocarcinoma cells to cell death. We employed malignant cholangiocarcinoma cell lines and used embelin to antagonize XIAP protein. Embelin treatment resulted in decreased XIAP protein levels by 8 hours of treatment with maximal effect at 16 hours in KMCH and Mz-ChA-1 …

Kinetic And Structural Characterization Of Tunnel-Perturbing Mutants In Bradyrhizobium Japonicum Proline Utilization A, Benjamin W. Arentson, Min Luo, Travis A. Pemberton, John J. Tanner, Donald F. Becker

Department of Biochemistry: Faculty Publications

Proline utilization A from Bradyrhizobium japonicum (BjPutA) is a bifunctional flavoenzyme that catalyzes the oxidation of proline to glutamate using fused proline dehydrogenase (PRODH) and Δ¹-pyrroline-5-carboxylate dehydrogenase (P5CDH) domains. Recent crystal structures and kinetic data suggest an intramolecular channel connects the two active sites, promoting substrate channeling of the intermediate Δ¹-pyrroline-5-carboxylate/glutamate-γ-semialdehyde (P5C/GSA). In this work, the structure of the channel was explored by inserting large side chain residues at four positions along the channel in BjPutA. Kinetic analysis of the different mutants revealed replacement of D779 with Tyr (D779Y) or Trp (D779W) significantly decreased the overall …

Proline Biosynthesis Is Required For Endoplasmic Reticulum Stress Tolerance In Saccharomyces Cerevisiae, Xinwen Liang, M. B. Dickman, Donald F. Becker

Department of Biochemistry: Faculty Publications

Background: Proline is an important amino acid for stress resistance in different organisms.

Results: Depletion of proline biosynthesis disrupts redox homeostasis and increases sensitivity to endoplasmic reticulum (ER) stress in yeast.

Conclusion: Proline biosynthesis is critical for maintaining the intracellular redox environment and the UPR during ER stress.

Significance: Proline metabolism is shown to have an important role in ER stress tolerance that was previously unknown.

Protein/Protein Interactions In The Mammalian Heme Degradation Pathway: Heme Oxygenase-2, Cytochrome P450 Reductase, And Biliverdin Reductase, Andrea L. M. Spencer, Ireena Bagai, Donald F. Becker, Erik R. P. Zuiderweg, Stephen W. Ragsdale

Department of Biochemistry: Faculty Publications

Heme oxygenase (HO) catalyzes the rate-limiting step in the O₂- dependent degradation of heme to biliverdin, CO, and iron with electrons delivered from NADPH via cytochrome P450 reductase (CPR). Biliverdin reductase (BVR) then catalyzes conversion of bili­verdin to bilirubin. We describe mutagenesis combined with kinetic, spectroscopic (fluorescence and NMR), surface plasmon resonance, cross-linking, gel filtration, and analytical ultracentrifugation studies aimed at evaluating interactions of HO-2 with CPR and BVR. Based on these results, we propose a model in which HO-2 and CPR form a dynamic ensemble of complex(es) that precede formation of the productive electron transfer complex. The …