Biology Commons^™

Acetyl Coa Carboxylase Inactivation And Meiotic Maturation In Mouse Oocytes, Deepa S. Valsangkar, Stephen M. Downs

Biological Sciences Faculty Research and Publications

In mouse oocytes, meiotic induction by pharmacological activation of PRKA (adenosine monophosphate-activated protein kinase; formerly known as AMPK) or by hormones depends on stimulation of fatty acid oxidation (FAO). PRKA stimulates FAO by phosphorylating and inactivating acetyl CoA carboxylase (ACAC; formerly ACC), leading to decreased malonyl CoA levels and augmenting fatty-acid transport into mitochondria. We investigated a role for ACAC inactivation in meiotic resumption by testing the effect of two ACAC inhibitors, CP-640186 and Soraphen A, on mouse oocytes maintained in meiotic arrest in vitro. These inhibitors significantly stimulated the resumption of meiosis in arrested cumulus cell-enclosed oocytes, denuded oocytes, …

Quinol Oxidase Encoded By Cyoabcd In Rhizobium Etli Cfn42 Is Regulated By Actsr And Is Crucial For Growth At Low Ph Or Low Iron Conditions, Zachary Ryan Lunak, K. Dale Noel

Biological Sciences Faculty Research and Publications

Rhizobium etli aerobically respires with several terminal oxidases. The quinol oxidase (Cyo) encoded by cyoABCD is needed for efficient adaptation to low oxygen conditions and cyo transcription is upregulated at low oxygen. This study sought to determine how transcription of the cyo operon is regulated. The 5′ sequence upstream of cyo was analysed in silico and revealed putative binding sites for ActR of the ActSR two-component regulatory system. The expression of cyo was decreased in an actSR mutant regardless of the oxygen condition. As ActSR is known to be important for growth under low pH in another rhizobial species, the …

The Tumor Suppressor Hhex Inhibits Axon Growth When Prematurely Expressed In Developing Central Nervous System Neurons, Matthew T. Simpson, Ishwariya Venkatesh, Ben L. Callif, Laura K. Thiel, Denise M. Coley, Kristen N. Winsor, Zimei Wang, Audra A. Kramer, Jessica K. Lerch, Murray G. Blackmore

Biological Sciences Faculty Research and Publications

Neurons in the embryonic and peripheral nervoussystem respond to injury by activating transcriptional programs supportive of axon growth, ultimately resulting in functional recovery. In contrast, neurons in the adult central nervous system (CNS) possess a limited capacity to regenerate axons after injury, fundamentally constraining repair. Activating pro-regenerative gene expression in CNS neurons is a promising therapeutic approach, but progress is hampered by incomplete knowledge of the relevant transcription factors. An emerging hypothesis is that factors implicated in cellular growth and motility outside the nervous system may also control axon growth in neurons. We therefore tested sixty-nine transcription factors, previously identified …

Pervasive And Strong Effects Of Plants On Soil Chemistry: A Meta-Analysis Of Individual Plant ‘Zinke’ Effects, Bonnie G. Waring, Leonor Álvarez-Cansino, Kathryn E. Barry, Kristen K. Becklund, Sarah Dale, Maria G. Gei, Adrienne B. Keller, Omar R. Lopez, Lars Markesteijn, Scott A. Mangan, Charlotte E. Riggs, Maria Elizabeth Rodríguez-Ronderos, R. Max Segnitz, Stefan A. Schnitzer, Jennifer S. Powers

Biological Sciences Faculty Research and Publications

Plant species leave a chemical signature in the soils below them, generating fine-scale spatial variation that drives ecological processes. Since the publication of a seminal paper on plant-mediated soil heterogeneity by Paul Zinke in 1962, a robust literature has developed examining effects of individual plants on their local environments (individual plant effects). Here, we synthesize this work using meta-analysis to show that plant effects are strong and pervasive across ecosystems on six continents. Overall, soil properties beneath individual plants differ from those of neighbours by an average of 41%. Although the magnitudes of individual plant effects exhibit weak relationships with …

Into The Light: Diurnality Has Evolved Multiple Times In Geckos, Tony Gamble, E. Greenbaum, Todd R. Jackman, Aaron M. Bauer

Biological Sciences Faculty Research and Publications

Geckos are the only major lizard group consisting mostly of nocturnal species. Nocturnality is presumed to have evolved early in gecko evolution and geckos possess numerous adaptations to functioning in low light and at low temperatures. However, not all gecko species are nocturnal and most diurnal geckos have their own distinct adaptations to living in warmer, sunlit environments. We reconstructed the evolution of gecko activity patterns using a newly generated time-calibrated phylogeny. Our results provide the first phylogenetic analysis of temporal activity patterns in geckos and confirm an ancient origin of nocturnality at the root of the gecko tree. We …

Arabidopsis Azi1 Family Proteins Mediate Signal Mobilization For Systemic Defence Priming, Nicolas M. Cecchini, Kevin Steffes, Michael Schläppi, Andrew N. Gifford, Jean T. Greenberg

Biological Sciences Faculty Research and Publications

Priming is a major mechanism behind the immunological 'memory' observed during two key plant systemic defences: systemic acquired resistance (SAR) and induced systemic resistance (ISR). Lipid-derived azelaic acid (AZA) is a mobile priming signal. Here, we show that the lipid transfer protein (LTP)-like AZI1 and its closest paralog EARLI1 are necessary for SAR, ISR and the systemic movement and uptake of AZA in Arabidopsis. Imaging and fractionation studies indicate that AZI1 and EARLI1 localize to expected places for lipid exchange/movement to occur. These are the ER/plasmodesmata, chloroplast outer envelopes and membrane contact sites between them. Furthermore, these LTP-like proteins form …

Shell Neurons Of The Master Circadian Clock Coordinate The Phase Of Tissue Clocks Throughout The Brain And Body, Jennifer A. Evans, Ting-Chung Suen, Ben L. Callif, Andrew S. Mitchell, Oscar Castanon-Cervantes, Kimberly M. Baker, Ian Kloehn, Kenkichi Baba, Brett J.W. Teubner, J. Christopher Ehlen, Ketema N. Paul, Timothy J. Bartness, Gianluca Tosini, Tanya Leise, Alec J. Davidson

Biological Sciences Faculty Research and Publications

Background: Daily rhythms in mammals are programmed by a master clock in the suprachiasmatic nucleus (SCN). The SCN contains two main compartments (shell and core), but the role of each region in system-level coordination remains ill defined. Herein, we use a functional assay to investigate how downstream tissues interpret region-specific outputs by using in vivo exposure to long day photoperiods to temporally dissociate the SCN. We then analyze resulting changes in the rhythms of clocks located throughout the brain and body to examine whether they maintain phase synchrony with the SCN shell or core. Results: Nearly all of the 17 …

Quantitative Detection Of Syntrophic Fatty Acid-Degrading Bacterial Communities In Methanogenic Environments, Prince Peter Mathai, Daniel Zitomer, James Maki

Biological Sciences Faculty Research and Publications

In methanogenic habitats, volatile fatty acids (VFA), such as propionate and butyrate, are major intermediates in organic matter degradation. VFA are further metabolized to H2, acetate and CO2 by syntrophic fatty acid-degrading bacteria (SFAB) in association with methanogenic archaea. Despite their indispensable role in VFA degradation, little is known about SFAB abundance and their environmental distribution. To facilitate ecological studies, we developed four novel genus-specific quantitative PCR (qPCR) assays, with primer sets targeting known SFAB: Syntrophobacter, Smithella, Pelotomaculum and Syntrophomonas. Primer set specificity was confirmed using in silico and experimental (target controls, clone libraries and melt-curve analysis) …

Aversive Stimuli Drive Drug Seeking In A State Of Low Dopamine Tone, Robert C. Twining, Daniel S. Wheeler, Amanda L. Ebben, Andre J. Jacobsen, Mykel A. Robble, John R. Mantsch, Robert A. Wheeler

Biological Sciences Faculty Research and Publications

Background

Stressors negatively impact emotional state and drive drug seeking, in part, by modulating the activity of the mesolimbic dopamine system. Unfortunately, the rapid regulation of dopamine signaling by the aversive stimuli that cause drug seeking is not well characterized. In a series of experiments, we scrutinized the subsecond regulation of dopamine signaling by the aversive stimulus, quinine, and tested its ability to cause cocaine seeking. Additionally, we examined the midbrain regulation of both dopamine signaling and cocaine seeking by the stress-sensitive peptide, corticotropin releasing factor (CRF).

Methods

Combining fast-scan cyclic voltammetry with behavioral pharmacology, we examined the effect of …

Inactivation Of Mandelate Racemase By 3-Hydroxypyruvate Reveals A Potential Mechanistic Link Between Enzyme Superfamilies, Mitesh Nagar, Brittney N. Wyatt, Martin St. Maurice, Stephen L. Bearne

Biological Sciences Faculty Research and Publications

Mandelate racemase (MR), a member of the enolase superfamily, catalyzes the Mg²⁺-dependent interconversion of the enantiomers of mandelate. Several α-keto acids are modest competitive inhibitors of MR [e.g., mesoxalate (K_i = 1.8 ± 0.3 mM) and 3-fluoropyruvate (K_i = 1.3 ± 0.1 mM)], but, surprisingly, 3-hydroxypyruvate (3-HP) is an irreversible, time-dependent inhibitor (k_inact/K_I = 83 ± 8 M^–1 s^–1). Protection from inactivation by the competitive inhibitor benzohydroxamate, trypsinolysis and electrospray ionization tandem mass spectrometry analyses, and X-ray crystallographic studies reveal that 3-HP undergoes Schiff-base formation with …

Daily Environmental Conditions Determine The Competition–Facilitation Balance For Plant Water Status, Alexandra Wright, Stefan A. Schnitzer, Peter B. Reich

Biological Sciences Faculty Research and Publications

1. Plants compete with their neighbours for a finite set of limiting resources, and this decreases individual plant performance, growth and survival. However, neighbouring plants also affect each other in positive ways.
2. Positive facilitative effects can occur when neighbouring plants ameliorate harsh abiotic conditions (temperature, wind and high irradiation). Thus, when environmental conditions are severe, the importance of facilitation may increase. The co‐occurrence and masking effects of competition and facilitation among neighbouring plants have made it difficult to tease them apart in the past.
3. We planted bur oak acorns (Quercus macrocarpa) into an experimental diversity gradient in a central …

The Melanocortin-4 Receptor Integrates Circadian Light Cues And Metabolism, Deanna M. Arble, Jenna Holland, Nickki Ottaway, Joyce Sorrell, Joshua W. Pressler, Rachel Morano, Stephen C. Woods, Randy J. Seeley, James P. Herman, Darleen A. Sandoval, Diego Perez-Tilve

Biological Sciences Faculty Research and Publications

The melanocortin system directs diverse physiological functions from coat color to body weight homoeostasis. A commonality among melanocortin-mediated processes is that many animals modulate similar processes on a circannual basis in response to longer, summer days, suggesting an underlying link between circadian biology and the melanocortin system. Despite key neuroanatomical substrates shared by both circadian and melanocortin-signaling pathways, little is known about the relationship between the two. Here we identify a link between circadian disruption and the control of glucose homeostasis mediated through the melanocortin-4 receptor (Mc4r). Mc4r-deficient mice exhibit exaggerated circadian fluctuations in baseline blood glucose and glucose tolerance. …

Restriction Site-Associated Dna Sequencing (Rad-Seq) Reveals An Extraordinary Number Of Transitions Among Gecko Sex-Determining Systems, Tony Gamble, Jessi Coryell, Tariq Ezaz, Joshua Lynch

Biological Sciences Faculty Research and Publications

Sex chromosomes have evolved many times in animals and studying these replicate evolutionary “experiments” can help broaden our understanding of the general forces driving the origin and evolution of sex chromosomes. However this plan of study has been hindered by the inability to identify the sex chromosome systems in the large number of species with cryptic, homomorphic sex chromosomes. Restriction site-associated DNA sequencing (RAD-seq) is a critical enabling technology that can identify the sex chromosome systems in many species where traditional cytogenetic methods have failed. Using newly generated RAD-seq data from 12 gecko species, along with data from the literature, …

Metabolic Effects Of Bariatric Surgery In Mouse Models Of Circadian Disruption, Deanna M. Arble, Darleen A. Sandoval, Fred W. Turek, Stephen C. Woods, Randy J. Seeley

Biological Sciences Faculty Research and Publications

Background/Objectives:

Mounting evidence supports a link between circadian disruption and metabolic disease. Humans with circadian disruption (for example, night-shift workers) have an increased risk of obesity and cardiometabolic diseases compared with the non-disrupted population. However, it is unclear whether the obesity and obesity-related disorders associated with circadian disruption respond to therapeutic treatments as well as individuals with other types of obesity.

Subjects/Methods:

Here, we test the effectiveness of the commonly used bariatric surgical procedure, Vertical Sleeve Gastrectomy (VSG), in mouse models of genetic and environmental circadian disruption.

Results:

VSG led to a reduction in body weight and fat mass in …

Detection Of Multi-Drug Resistant Escherichia Coli In The Urban Waterways Of Milwaukee, Wi, Anthony D. Kappell, Maxwell S. Denies, Neha H. Ahuja, Nathan A. Ledeboer, Ryan J. Newton, Krassimira R. Hristova

Biological Sciences Faculty Research and Publications

Urban waterways represent a natural reservoir of antibiotic resistance which may provide a source of transferable genetic elements to human commensal bacteria and pathogens. The objective of this study was to evaluate antibiotic resistance of Escherichia coli isolated from the urban waterways of Milwaukee, WI compared to those from Milwaukee sewage and a clinical setting in Milwaukee. Antibiotics covering 10 different families were utilized to determine the phenotypic antibiotic resistance for all 259 E. coli isolates. All obtained isolates were determined to be multi-drug resistant. The E. coli isolates were also screened for the presence of the genetic determinants of …

Gene Mdpc Plays A Regulatory Role In The Methyl-Tert-Butyl Ether Degradation Pathway Of Methylibium Petroleiphilum Strain Pm1, Geetika Joshi, Radomir Schmidt, Kate M. Scow, Michael S. Denison, Krassimira R. Hristova

Biological Sciences Faculty Research and Publications

Among the few bacteria known to utilize methyl tert-butyl ether (MTBE) as a sole carbon source, Methylibium petroleiphilum PM1 is a well-characterized organism with a sequenced genome; however, knowledge of the genetic regulation of its MTBE degradation pathway is limited. We investigated the role of a putative transcriptional activator gene, mdpC, in the induction of MTBE-degradation genes mdpA (encoding MTBE monooxygenase) and mdpJ (encoding tert-butyl alcohol hydroxylase) of strain PM1 in a gene-knockout mutant mdpC⁻. We also utilized quantitative reverse transcriptase PCR assays targeting genes mdpA, mdpJ and mdpC to determine the effects of …

Genetic And Molecular Analysis Of Dec-11 In C. Elegans' Intestinal Pacemaker Activity, Adele Joan Gordon

Master's Theses (2009 -)

Rhythmic behaviors are ubiquitous phenomena in plant and animal phyla. Ultradian rhythmic behaviors occur with a period of less than 24 hours and include such rhythmic behaviors as the beating of the heart and peristalsis in the gut. The nematode C. elegans exhibits three well-characterized ultradian rhythmic behaviors: ovulation, pharyngeal pumping, and the defecation motor program (DMP). The DMP occurs every ~45 seconds in wild-type worms and comprises three distinct muscle contractions: a posterior body contraction (pBoc), an anterior body contraction (aBoc), and an enteric muscle contraction (Emc), which is coupled to expulsion (Exp). The rhythmicity of the DMP is …

Weekly Versus Monthly Testosterone Administration On Fast And Slow Skeletal Muscle Fibers In Older Adult Males, Robert H. Fitts, James R. Peters, E. Lichar Dillon, William J. Durham, Melinda A. Sheffield-Moore, Randall J. Urban

Biological Sciences Faculty Research and Publications

Context: In older adults, loss of mobility due to sarcopenia is exacerbated in men with low serum T. T replacement therapy is known to increase muscle mass and strength, but the effect of weekly (WK) vs monthly (MO) administration on specific fiber types is unknown.

Objective: To determine the efficacy of WK vs MO T replacement on the size and functional capacity of individual fast and slow skeletal muscle fiber types.

Design, Setting, and Patients:

Subjects were randomized into a 5-month, double-blind, placebo-controlled trial. All subjects (ages, 61–71 y) were community-dwelling men who had T levels < 500 ng/dL.

Intervention: Subjects were dosed …

Mechanisms Underlying Weight Loss And Metabolic Improvements In Rodent Models Of Bariatric Surgery, Deanna M. Arble, Darleen A. Sandoval, Randy J. Seeley

Biological Sciences Faculty Research and Publications

Obesity is a growing health risk with few successful treatment options and fewer still that target both obesity and obesity-associated comorbidities. Despite ongoing scientific efforts, the most effective treatment option to date was not developed from basic research but by surgeons observing outcomes in the clinic. Bariatric surgery is the most successful treatment for significant weight loss, resolution of type 2 diabetes and the prevention of future weight gain. Recent work with animal models has shed considerable light on the molecular underpinnings of the potent effects of these ‘metabolic’ surgical procedures. Here we review data from animal models and how …

Intrinsically Disordered C-Terminal Tails Of E. Coli Single-Stranded Dna Binding Protein Regulate Cooperative Binding To Single-Stranded Dna, Alexander G. Kozlov, Elizabeth A. Weiland, Anuradha Mittal, Vince Waldman, Edwin Antony, Nicole Fazio, Rohit V. Pappu, Timothy M. Lohman

Biological Sciences Faculty Research and Publications

The homotetrameric Escherichia coli single-stranded DNA binding protein (SSB) plays a central role in DNA replication, repair and recombination. E. coli SSB can bind to long single-stranded DNA (ssDNA) in multiple binding modes using all four subunits [(SSB)₆₅ mode] or only two subunits [(SSB)₃₅ binding mode], with the binding mode preference regulated by salt concentration and SSB binding density. These binding modes display very different ssDNA binding properties with the (SSB)₃₅ mode displaying highly cooperative binding to ssDNA. SSB tetramers also bind an array of partner proteins, recruiting them to their sites of action. This is …

Unique Competitive Effects Of Lianas And Trees In A Tropical Forest Understory, Alexandra Wright, Michael F. Tobin, Scott A. Mangan, Stefan A. Schnitzer

Biological Sciences Faculty Research and Publications

Lianas are an important component of tropical forests, contributing up to 25 % of the woody stems and 35 % of woody species diversity. Lianas invest less in structural support but more in leaves compared to trees of similar biomass. These physiological and morphological differences suggest that lianas may interact with neighboring plants in ways that are different from similarly sized trees. However, the vast majority of past liana competition studies have failed to identify the unique competitive effects of lianas by controlling for the amount of biomass removed. We assessed liana competition in the forest understory over the course …

Evolution Of The Antisense Overlap Between Genes For Thyroid Hormone Receptor And Rev-Erbα And Characterization Of An Exonic G-Rich Element That Regulates Splicing Of Trα2 Mrna, Stephen H. Munroe, Christopher H. Morales, Tessa H. Duyck, Paul D. Waters

Biological Sciences Faculty Research and Publications

The α-thyroid hormone receptor gene (TRα) codes for two functionally distinct proteins: TRα1, the α-thyroid hormone receptor; and TRα2, a non-hormone-binding variant. The final exon of TRα2 mRNA overlaps the 3’ end of Rev-erbα mRNA, which encodes another nuclear receptor on the opposite strand of DNA. To understand the evolution of this antisense overlap, we sequenced these genes and mRNAs in the platypus Orthorhynchus anatinus. Despite its strong homology with other mammals, the platypus TRα/Rev-erbα locus lacks elements essential for expression of TRα2. Comparative analysis suggests that alternative splicing of TRα2 mRNA expression evolved in a stepwise fashion before …

No Evidence That Elevated Co2 Gives Tropical Lianas An Advantage Over Tropical Trees, David C. Marvin, Klaus Winter, Robyn J. Burnham, Stefan A. Schnitzer

Biological Sciences Faculty Research and Publications

Recent studies indicate that lianas are increasing in size and abundance relative to trees in neotropical forests. As a result, forest dynamics and carbon balance may be altered through liana‐induced suppression of tree growth and increases in tree mortality. Increasing atmospheric CO₂ is hypothesized to be responsible for the increase in neotropical lianas, yet no study has directly compared the relative response of tropical lianas and trees to elevated CO₂. We explicitly tested whether tropical lianas had a larger response to elevated CO₂ than co‐occurring tropical trees and whether seasonal drought alters the response of either …

A Quinol Oxidase, Encoded By Cyoabcd, Is Utilized To Adapt To Lower O2 Concentrations In Rhizobium Etli Cfn42, Zachary Ryan Lunak, K. Dale Noel

Biological Sciences Faculty Research and Publications

Bacteria have branched aerobic respiratory chains that terminate at different terminal oxidases. These terminal oxidases have varying properties such as their affinity for oxygen, transcriptional regulation and proton pumping ability. The focus of this study was a quinol oxidase encoded by cyoABCD. Although this oxidase (Cyo) is widespread among bacteria, not much is known about its role in the cell, particularly in bacteria that contain both cytochrome c oxidases and quinol oxidases. Using Rhizobium etli CFN42 as a model organism, a cyo mutant was analysed for its ability to grow in batch cultures at high (21 % O2) and low …

Type I Interferons Link Viral Infection To Enhanced Epithelial Turnover And Repair, Lulu Sun, Hiroyuki Miyoshi, Sofia Origanti, Timothy J. Nice, Alexandra C. Barger, Nicholas A. Manieri, Leslie A. Fogel, Anthony R. French, David Piwnica-Worms, Helen Piwnica-Worms, Herbert W. Virgin, Deborah J. Lenschow, Thaddeus S. Stappenbeck

Biological Sciences Faculty Research and Publications

The host immune system functions constantly to maintain chronic commensal and pathogenic organisms in check. The consequences of these immune responses on host physiology are as yet unexplored, and may have long-term implications in health and disease. We show that chronic viral infection increases epithelial turnover in multiple tissues, and the antiviral cytokines type I interferons (IFNs) mediate this response. Using a murine model with persistently elevated type I IFNs in the absence of exogenous viral infection, the Irgm1^−/− mouse, we demonstrate that type I IFNs act through nonepithelial cells, including macrophages, to promote increased epithelial turnover and wound …

Different Sites Of Alcohol Action In The Nmda Receptor Glun2a And Glun2b Subunits, Yulin Zhao, Hong Ren, Donard S. Dwyer, Robert W. Peoples

Biological Sciences Faculty Research and Publications

The NMDA receptor is a major target of alcohol action in the CNS, and recent behavioral and cellular studies have pointed to the importance of the GluN2B subunit in alcohol action. We and others have previously characterized four amino acid positions in the third and fourth membrane-associated (M) domains of the NMDA receptor GluN2A subunit that influence both ion channel gating and alcohol sensitivity. In this study, we found that substitution mutations at two of the four corresponding positions in the GluN2B subunit, F637 and G826, influence ethanol sensitivity and ion channel gating. Because position 826 contains a glycine residue …

Liana Competition With Tropical Trees Varies Seasonally But Not With Tree Species Identity, Leonor Álvarez-Cansino, Stefan A. Schnitzer, Joseph P. Reid, Jennifer S. Powers

Biological Sciences Faculty Research and Publications

Lianas in tropical forests compete intensely with trees for above‐ and belowground resources and limit tree growth and regeneration. Liana competition with adult canopy trees may be particularly strong, and, if lianas compete more intensely with some tree species than others, they may influence tree species composition. We performed the first systematic, large‐scale liana removal experiment to assess the competitive effects of lianas on multiple tropical tree species by measuring sap velocity and growth in a lowland tropical forest in Panama. Tree sap velocity increased 60% soon after liana removal compared to control trees, and tree diameter growth increased 25% …

The Ecology Of Lianas In Tropical Forests, Stefan A. Schnitzer

Biological Sciences Faculty Research and Publications

No abstract provided.

Fouling And Its Next Generation Management: A Perspective, Daniel Rittschof, Christina Chai, Serena Lay Ming Teo, James Maki

Biological Sciences Faculty Research and Publications

The last 50 years of fouling research and management taught us that indiscriminate use of toxic approaches damages ecosystem services of estuaries and oceans critical to man’s existence. Next generation environmentally benign management requires knowledge of the fouling process and an understanding of the consequences of different management options. An intermediate step may be additives that fit with existing business models and distribution systems, but that carry a much reduced environmental footprint. Subsequently, the evolution of a next generation hull fouling management system with limited toxicity easy clean surfaces should replace or augment the existing commercial easy-release coatings. These new …

The Role Of Biotin And Oxamate In The Carboxyltransferase Reaction Of Pyruvate Carboxylase, Adam D. Lietzan, Yi Lin, Martin St. Maurice

Biological Sciences Faculty Research and Publications

Pyruvate carboxylase (PC) is a biotin-dependent enzyme that catalyzes the MgATP-dependent carboxylation of pyruvate to oxaloacetate, an important anaplerotic reaction in central metabolism. During catalysis, carboxybiotin is translocated to the carboxyltransferase domain where the carboxyl group is transferred to the acceptor substrate, pyruvate. Many studies on the carboxyltransferase domain of PC have demonstrated an enhanced oxaloacetate decarboxylation activity in the presence of oxamate and it has been shown that oxamate accepts a carboxyl group from carboxybiotin during oxaloacetate decarboxylation. The X-ray crystal structure of the carboxyltransferase domain from Rhizobium etli PC reveals that oxamate is positioned in the active site …