Biochemistry, Biophysics, and Structural Biology Commons^™

Copper Transport Activity Of Yeast Ctr1 Is Down-Regulated Via Its C Terminus In Response To Excess Copper, Xiaobin Wu, Devis Sinani, Heejeong Kim, Jaekwon Lee

Department of Biochemistry: Faculty Publications

Copper is an essential yet toxic trace element. The Ctr1 family of proteins plays a critical role for copper uptake in eukaryotes. However, the mechanisms of action of Ctr1 are largely unknown. Our previous data demonstrated that copper transport induces conformational changes in the cytosolic C terminus of the yeast Saccharomyces cerevisiae Ctr1. To define the physiological significance of this molecular event and gain better insights into the mechanism of Ctr1-mediated copper uptake, we have characterized the functional roles of the Ctr1 C terminus.ACtr1 mutant lacking the entire C-terminal cytosolic tail is functional in high affinity copper uptake; however, yeast …

Contribution Of Impaired Myocardial Insulin Signaling To Mitochondrial Dysfunction And Oxidative Stress In The Heart, Sihem Boudina, Heiko Bugger, Sandra Sena, Brian T. O'Neill, Vlad G. Zaha, Olesya Ilkun, Jordan J. Wright, Pradip K. Mazumber, Eric Palfreyman, Timothy J. Tidwell, Heather Theobald, Oleh Khalimonchuk, Benjamin Wayment, Xiaoming Sheng, Kenneth J. Rodnick, Ryan Centini, Dong Chen, Sheldon E. Litwin, Bart E. Weimer, E. Dale Abel

Department of Biochemistry: Faculty Publications

Background—Diabetes-associated cardiac dysfunction is associated with mitochondrial dysfunction and oxidative stress, which may contribute to LV dysfunction. The contribution of altered myocardial insulin action, independently of associated changes in systemic metabolism is incompletely understood. The present study tested the hypothesis that perinatal loss of insulin signaling in the heart impairs mitochondrial function.

Methods and Results—In 8-week-old mice with cardiomyocyte deletion of insulin receptors (CIRKO), inotropic reserves were reduced and mitochondria manifested respiratory defects for pyruvate that was associated with proportionate reductions in catalytic subunits of pyruvate dehydrogenase. Progressive age-dependent defects in oxygen consumption and ATP synthesis with the substrates glutamate …

Sdh5, A Gene Required For Flavination Of Succinate Dehydrogenase, Is Mutated In Paraganglioma, Huai-Xiang Hao, Oleh Khalimonchuk, Margit Schraders, Noah Dephoure, Jean-Pierre Bayley, Henricus Kunst, Peter Devilee, Cor W.R.J. Cremers, Joshua D. Schiffman, Brandon G. Bentz, Steven P. Gygi, Dennis R. Winge, Hannie Kremer, Jared Rutter

Department of Biochemistry: Faculty Publications

Mammalian mitochondria contain about 1100 proteins, nearly 300 of which are uncharacterized. Given the well-established role of mitochondrial defects in human disease, functional characterization of these proteins may shed new light on disease mechanisms. Starting with yeast as a model system, we investigated an uncharacterized but highly conserved mitochondrial protein (named here Sdh5). Both yeast and human Sdh5 interact with the catalytic subunit of the succinate dehydrogenase (SDH) complex, a component of both the electron transport chain and the tricarboxylic acid cycle. Sdh5 is required for SDH-dependent respiration and for Sdh1 flavination (incorporation of the flavin adenine dinucleotide cofactor). Germline …

Chemchains: A Platform For Simulation And Analysis Of Biochemical Networks Aimed To Laboratory Scientists, Tomáš Helikar, Jim A. Rogers

Department of Biochemistry: Faculty Publications

Background: New mathematical models of complex biological structures and computer simulation software allow modelers to simulate and analyze biochemical systems in silico and form mathematical predictions. Due to this potential predictive ability, the use of these models and software has the possibility to compliment laboratory investigations and help refine, or even develop, new hypotheses. However, the existing mathematical modeling techniques and simulation tools are often difficult to use by laboratory biologists without training in high-level mathematics, limiting their use to trained modelers.

Results: We have developed a Boolean network-based simulation and analysis software tool, ChemChains, which combines the advantages of …

Ulk-Atg13-Fip200 Complexes Mediate Mtor Signaling To The Autophagy Machinery, Chang Hwa Jung, Chang Bong Jun, Seung-Hyun Ro, Young-Mi Kim, Neil Michael Otto, Jing Cao, Mondira Kundu, Do-Hyung Kim

Department of Biochemistry: Faculty Publications

Autophagy, the starvation-induced degradation of bulky cytosolic components, is up-regulated in mammalian cells when nutrient supplies are limited. Although mammalian target of rapamycin (mTOR) is known as the key regulator of autophagy induction, the mechanism by which mTOR regulates autophagy has remained elusive. Here, we identify that mTOR phosphorylates a mammalian homologue of Atg13 and the mammalian Atg1 homologues ULK1 and ULK2. The mammalian Atg13 binds both ULK1 and ULK2 and mediates the interaction of the ULK proteins with FIP200. The binding of Atg13 stabilizes and activates ULK and facilitates the phosphorylation of FIP200 by ULK, whereas knockdown of Atg13 …

Editorial: Dietary Lipid Absorption, Concetta Dirusso, Paul N. Black

Department of Biochemistry: Faculty Publications

The composition of dietary fat influences tissue fatty acid composition, which in turn impacts cellular function through a number of different processes. This includes changes in signaling, lipid metabolism, and transcriptional activities that normally function to maintain intracellular fatty acid homeostasis. The consumption of high levels of dietary fat in excess of caloric expenditure is linked with obesity and the disruption of normal homeostatic mechanisms governing lipid metabolism. Data from the Centers for Disease Control and Prevention show that obesity (defined as a BMI≥30) represents a considerable health concern in the United States. Of particular note is that for adult …

Global Analysis Of Gene Expression Changes During Retinoic Acid-Induced Growth Arrest And Differentiation Of Melanoma: Comparison To Differentially Expressed Genes In Melanocytes Vs Melanoma, Mary H. Estler, Goran Boskovic, James Denvir, Sarah Miles, Donald A. Primerano, Richard M. Niles

Biochemistry and Microbiology

BACKGROUND: The incidence of malignant melanoma has significantly increased over the last decade. Some of these malignancies are susceptible to the growth inhibitory and pro-differentiating effects of all-trans-retinoic acid (RA). The molecular changes responsible for the biological activity of RA in melanoma are not well understood.

RESULTS: In an analysis of sequential global gene expression changes during a 4-48 h RA treatment of B16 mouse melanoma cells, we found that RA increased the expression of 757 genes and decreased the expression of 737 genes. We also compared the gene expression profile (no RA treatment) between non-malignant melan-a mouse melanocytes and …

Aminoacyl-Trna Synthetase Complexes: Molecular Multitasking Revealed, Corinne D. Hausmann, Michael Ibba

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

The accurate synthesis of proteins, dictated by the corresponding nucleotide sequence encoded in mRNA, is essential for cell growth and survival. Central to this process are the aminoacyl-tRNA synthetases (aaRSs), which provide amino acid substrates for the growing polypeptide chain in the form of aminoacyl-tRNAs. The aaRSs are essential for coupling the correct amino acid and tRNA molecules, but are also known to associate in higher order complexes with proteins involved in processes beyond translation. Multiprotein complexes containing aaRSs are found in all three domains of life playing roles in splicing, apoptosis, viral assembly, and regulation of transcription and translation. …

Structural And Functional Mapping Of The Archaeal Multi-Aminoacyl-Trna Synthetase Complex, Corinne D. Hausmann, Michael Ibba

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Methanothermobacter thermautotrophicus contains a multi-aminoacyl-tRNA synthetase complex (MSC) of LysRS, LeuRS and ProRS. Elongation factor (EF) 1A also associates to the MSC, with LeuRS possibly acting as a core protein. Analysis of the MSC revealed that LysRS and ProRS specifically interact with the idiosyncratic N- and C- termini of LeuRS, respectively. EF-1A instead interacts with the inserted CP1 proofreading domain, consistent with models for post-transfer editing by class I synthetases such as LeuRS. Together with previous genetic data, these findings show that LeuRS plays a central role in mediating interactions within the archaeal MSC by acting as a core scaffolding …

Emergent Decision-Making In Biological Signal Transduction Networks, Tomáš Helikar, John Konvalina, Jack Heidel, Jim A. Rogers

Department of Biochemistry: Faculty Publications

The complexity of biochemical intracellular signal transduction networks has led to speculation that the high degree of interconnectivity that exists in these networks transforms them into an information processing network. To test this hypothesis directly, a large scale model was created with the logical mechanism of each node described completely to allow simulation and dynamical analysis. Exposing the network to tens of thousands of random combinations of inputs and analyzing the combined dynamics of multiple outputs revealed a robust system capable of clustering widely varying input combinations into equivalence classes of biologically relevant cellular responses. This capability was nontrivial in …

Monitoring Lys-TrnaLys Phosphatidylglycerol Transferase Activity, Michael Ibba

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

In some bacteria Lys-tRNA^Lys is used both in translation and for the specific addition of Lys to phosphatidylglycerol in the cytoplasmic membrane. This reaction is catalyzed by the membrane protein MprF, and the lysyl-phosphatidylglycerol formed contributes to the resistance of these bacteria to various cationic antibacterial molecules. Obtaining proteins and reconstituting an in vitro system mimicking membrane conditions is a major challenge to studying the function of membrane proteins, especially when labile substrates such as Lys-tRNA^Lys are required. Here we report methods to obtain a stable enriched membrane fraction containing MprF, and the techniques necessary to quantitatively monitor …

Functional Domains Of The Fatty Acid Transport Proteins: Studies Using Protein Chimeras, Concetta C. Dirusso, Dina Darwis, Thomas Obermeyer, Paul N. Black

Department of Biochemistry: Faculty Publications

Fatty acid transport proteins (FATP) function in fatty acid trafficking pathways, several of which have been shown to participate in the transport of exogenous fatty acids into the cell. Members of this protein family also function as acyl CoA synthetases with specificity towards very long chain fatty acids or bile acids. These proteins have two identifying sequence motifs: The ATP/AMP motif, an approximately 100 amino acid segment required for ATP binding and common to members of the adenylate-forming super family of proteins, and the FATP/VLACS motif that consists of approximately 50 amino acid residues and is restricted to members of …

Mapping The Functional Interaction Of Sco1 And Cox2 In Cytochrome Oxidase Biogenesis, Kevin Rigby, Paul A. Cobine, Oleh Khalimonchuk, Dennis R. Winge

Department of Biochemistry: Faculty Publications

Sco1 is implicated in the copper metallation of the Cu_A site in

Cox2 of cytochrome oxidase. The structure of Sco1 in the metallated

and apo-conformers revealed structural dynamics primarily

in an exposed region designated loop 8. The structural

dynamics of loop 8 in Sco1 suggests it may be an interface for

interactions with Cox17, the Cu(I) donor and/or Cox2. A series

of conserved residues in the sequence motif ²¹⁷KKYRVYF²²³ on

the leading edge of this loop are shown presently to be important

for yeast Sco1 function. Cells harboring Y219D, R220D, V221D,

and Y222D mutant Sco1 proteins failed …

Function And Redox State Of Mitochondrial Localized Cysteine-Rich Proteins Important In The Assembly Of Cytochrome C Oxidase, Oleh Khalimonchuk, Dennis R. Winge

Department of Biochemistry: Faculty Publications

The cytochrome c oxidase (CcO) complex of the mitochondrial respiratory chain exists within the mitochondrial inner membrane (IM). The biogenesis of the complex is a multi-faceted process requiring multiple assembly factors that function on both faces of the IM. Formation of the two copper centers of CcO occurs within the intermembrane space (IMS) and is dependent on assembly factors with critical cysteinyl thiolates. Two classes of assembly factors exist, one group being soluble IMS proteins and the second class being proteins tethered to the IM. A common motif in the soluble assembly factors is a duplicated Cx₉C sequence …

Pet191 Is A Cytochrome C Oxidase Assembly Factor In Saccharomyces Cerevisiae, Oleh Khalimonchuk, Kevin Rigby, Megan Bestwick, Fabien Pierrel, Paul A. Cobine, Dennis R. Winge

Department of Biochemistry: Faculty Publications

The twin-Cx₉C motif protein Pet191 is essential for cytochrome c oxidase maturation. The motif Cys residues are functionally important and appear to be present in disulfide linkages within a large oligomeric complex associated with the mitochondrial inner membrane. The import of Pet191 differs from that of other twin-Cx₉C motif class of proteins in being independent of the Mia40 pathway.

Coa2 Is An Assembly Factor For Yeast Cytochrome C Oxidase Biogenesis That Facilitates The Maturation Of Cox1, Fabien Pierrel, Oleh Khalimonchuk, Paul A. Cobine, Megan Bestwick, Dennis R. Winge

Department of Biochemistry: Faculty Publications

The assembly of cytochrome c oxidase (CcO) in yeast mitochondria is dependent on a new assembly factor designated Coa2. Coa2 was identified from its ability to suppress the respiratory deficiency of coa1 Δ and shy1 Δ cells. Coa1 and Shy1 function at an early step in maturation of the Cox1 subunit of CcO. Coa2 functions downstream of the Mss51-Coa1 step in Cox1 maturation and likely concurrent with the Shy1-related heme a₃ insertion into Cox1. Coa2 interacts with Shy1. Cells lacking Coa2 show a rapid degradation of newly synthesized Cox1. Rapid Cox1 proteolysis also occurs in shy1 Δ cells, suggesting …

Purification From Human Milk Of Matriptase Complexes With Secreted Serpins: Mechanism For Inhibition Of Matriptase Other Than Hai-1, I-Chu Tseng, Feng-Pai Chou, Sheng-Feng Su, Michael Oberst, Nandakumar Madayiputhiya, Ming-Shyue Lee, Jehng-Kang Wang, David E. Sloane, Michael Johnson, Chen-Yong Lin

Department of Biochemistry: Faculty Publications

Matriptase, a type 2 transmembrane serine protease, is predominately expressed by epithelial and carcinoma cells in which hepatocyte growth factor activator inhibitor 1 (HAI-1), a membrane-bound, Kunitz-type serine protease inhibitor, is also expressed. HAI-1 plays dual roles in the regulation of matriptase, as a conventional protease inhibitor and as a factor required for zymogen activation of matriptase. As a consequence, activation of matriptase is immediately followed by HAI-1-mediated inhibition, with the activated matriptase being sequestered into HAI-1 complexes. Matriptase is also expressed by peripheral blood leukocytes, such as monocytes and macrophages; however, in contrast to epithelial cells, monocytes and macrophages …

High-Throughput Screening For Fatty Acid Uptake Inhibitors In Humanized Yeast Identifies Atypical Antipsychotic Drugs That Cause Dyslipidemias, Hong Li, Paul N. Black, Aalap Chokshi, Angel Sandoval-Alvarez, Ravi Vatsyayan, Whitney Sealls, Concetta Dirusso

Department of Biochemistry: Faculty Publications

Fatty acids are implicated in the development of dyslipidemias, leading to type 2 diabetes and cardiovascular disease. We used a standardized small compound library to screen humanized yeast to identify compounds that inhibit fatty acid transport protein (FATP)-mediated fatty acid uptake into cells. This screening procedure used live yeast cells expressing human FATP2 to identify small compounds that reduced the import of a fluorescent fatty acid analog, 4,4-difluoro-5-methyl-4-bora-3a,4a-diaza-s-indacene-3-dodecanoic acid (C1-BODIPY-C12). The library used consisted of 2,080 compounds with known biological activities. Of these, ~1.8% reduced cell-associated C1-BODIPY-C12 fluorescence and were selected as potential inhibitors of human FATP2- mediated fatty acid …

Phenylalanyl-Trna Synthetase Editing Defects Result In Efficient Mistranslation Of Phenylalanine Codons As Tyrosine, Jiqiang Ling, Srujana S. Yadavalli, Michael Ibba

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Translational quality control is monitored at several steps, including substrate selection by aminoacyl-tRNA synthetases (aaRSs), and discrimination of aminoacyl-tRNAs by elongation factor Tu (EF-Tu) and the ribosome. Phenylalanyl-tRNA synthetase (PheRS) misactivates Tyr but is able to correct the mistake using a proofreading activity named editing. Previously we found that overproduction of editing-defective PheRS resulted in Tyr incorporation at Phe-encoded positions in vivo , although the misreading efficiency could not be estimated. This raised the question as to whether or not EF-Tu and the ribosome provide further proofreading mechanisms to prevent mistranslation of Phe codons by Tyr. Here we show that, …

An Aminoacyl-Trna Synthetase: Elongation Factor Complex For Substrate Channeling In Archaeal Translation, Corinne D. Hausmann, Mette Praetorius-Ibba, Michael Ibba

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Translation requires the specific attachment of amino acids to tRNAs by aminoacyl-tRNA synthetases (aaRSs) and the subsequent delivery of aminoacyl-tRNAs to the ribosome by elongation factor 1 alpha (EF-1α). Interactions between EF-1α and various aaRSs have been described in eukaryotes, but the role of these complexes remains unclear. To investigate possible interactions between EF-1α and other cellular components, a yeast two-hybrid screen was performed for the archaeon Methanothermobacter thermautotrophicus. EF-1α was found to form a stable complex with leucyl-tRNA synthetase (LeuRS; KD = 0.7 μ M). Complex formation had little effect on EF-1α activity, but increased the k_{cat …}

A New Strategy For Assessing Selenoprotein Function: Sirna Knockdown/Knock-In Targeting The 3'-Utr, Min-Hyuk Yoo, Xue-Ming Xu, Anton A. Turanov, Bradley A. Carlson, Vadim N. Gladyshev, Dolph L. Hatfield

Department of Biochemistry: Faculty Publications

Selenocysteine insertion into protein in mammalian cells requires RNA elements in the 3'-untranslated regions (3'-UTRs) of selenoprotein genes. The occurrence of these conserved sequences should make selenoproteins particularly amenable for knockdown/knock-in strategies to examine selenoprotein functions. Herein, we utilized the 3'-UTR of various selenoproteins to knock down their expression using siRNAs and then knock in expression using constructs containing mutations within the target region. Thioredoxin reductase 1 (TR1) knockdown in a mouse kidney cell line resulted in the cells growing about 10% more slowly, being more sensitive to UV radiation, and having increased apoptosis in response to UV than control …

Mechanistic Studies Of The Long Chain Acyl-Coa Synthetase Faa1p From Saccharomyces Cerevisiae, Hong Li, Elaina M. Melton, Steven Quackenbush, Concetta C. Dirusso, Paul N. Black

Department of Biochemistry: Faculty Publications

Long chain acyl-CoA synthetase (ACSL; fatty acid CoA ligase: AMP forming; EC 6.2.1.3) catalyzes the formation of acyl-CoA through a process, which requires fatty acid, ATP and coenzymeA as substrates. In the yeast Saccharomyces cerevisiae the principal ACSL is Faa1p (encoded by the FAA1 gene). The preferred substrates for this enzyme are cis-monounsaturated long chain fatty acids. Our previous work has shown Faa1p is a principal component of a fatty acid transport/activation complex that also includes the fatty acid transport protein Fat1p. In the present work hexameric histidine tagged Faa1p was purified to homogeneity through a two-step process in the …

Evidence For A Pro-Oxidant Intermediate In The Assembly Of Cytochrome Oxidase, Oleh Khalimonchuk, Amanda Bird, Dennis R. Winge

Department of Biochemistry: Faculty Publications

The hydrogen peroxide sensitivity of cells lacking two proteins,

Sco1 and Cox11, important in the assembly of cytochrome

c oxidase (CcO), is shown to arise from the transient accumulation

of a pro-oxidant heme A-Cox1 stalled intermediate. The

peroxide sensitivity of these cells is abrogated by a reduction in

either Cox1 expression or hemeAformation but exacerbated by

either enhanced Cox1 expression or heme A production arising

from overexpression of COX15. Sco1 and Cox11 are implicated

in the formation of the Cu_A and Cu_B sites of CcO, respectively.

The respective wild-type genes suppress the peroxide sensitivities

of sco1∆ …

Coa1 Links The Mss51 Post-Translational Function To Cox1 Cofactor Insertion In Cytochrome C Oxidase Assembly, Fabien Pierrel, Megan L. Bestwick, Paul A. Cobine, Oleh Khalimonchuk, Julia A. Cricco, Dennis R. Winge

Department of Biochemistry: Faculty Publications

The assembly of cytochrome c oxidase (CcO) in yeast mitochondria is shown to be dependent on a new assembly factor designated Coa1 that associates with the mitochondrial inner membrane. Translation of the mitochondrial-encoded subunits of CcO occurs normally in coa1Δ cells, but these subunits fail to accumulate. The respiratory defect in coa1Δ cells is suppressed by high-copy MSS51, MDJ1 and COX10. Mss51 functions in Cox1 translation and elongation, whereas Cox10 participates in the biosynthesis of heme a, a key cofactor of CcO. Respiration in coa1Δ and shy1Δ cells is enhanced when Mss51 and …

Functional Association Between Three Archaeal Aminoacyl-Trna Synthetases, Mette Praetorius-Ibba, Corinne D. Hausmann, Molly Paras, Theresa E. Rogers, Michael Ibba

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Aminoacyl-tRNA synthetases (aaRSs) are responsible for attaching amino acids to their cognate tRNAs during protein synthesis. In eukaryotes aaRSs are commonly found in multi-enzyme complexes, although the role of these complexes is still not completely clear. Associations between aaRSs have also been reported in archaea, including a complex between prolyl-(ProRS) and leucyl-tRNA synthetases (LeuRS) in Methanothermobacter thermautotrophicus that enhances tRNA^Pro aminoacylation. Yeast two-hybrid screens suggested that lysyl-tRNA synthetase (LysRS) also associates with LeuRS in M. thermautotrophicus. Co-purification experiments confirmed that LeuRS, LysRS, and ProRS associate in cell-free extracts. LeuRS bound LysRS and ProRS with a comparable K_{D …}

Aspartyl-Trna Synthetase Is The Target Of Peptidenucleotide Antibiotic Microcin C, Anastasia Metlitskaya, Teymur Kazakov, Aigar Kommer, Olga Pavlova, Mette Praetorius-Ibba, Michael Ibba, Igor Krasheninnkov, Vyacheslav Kolb, Inessa Khmel, Konstantin Severinov

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Microcin C is a ribosome-synthesized heptapeptide that contains a modified adenosine monophosphate covalently attached to the C-terminal aspartate. Microcin C is a potent inhibitor of bacterial cell growth. Based on the in vivo kinetics of inhibition of macromolecular synthesis, Microcin C targets translation, through a mechanism that remained undefined. Here, we show that Microcin C is a subject of specific degradation inside the sensitive cell. The product of degradation, a modified aspartyl-adenylate containing an N-acylphosphoramidate linkage, strongly inhibits translation by blocking the function of aspartyl-tRNA synthetase.

C To U Editing Stimulates A To I Editing In The Anticodon Loop Of A Cytoplasmic Threonyl Trna In Trypanosoma Brucei, Mary Anne T. Rubio, Frank L. Ragone, Kirk W. Gaston, Michael Ibba, Juan D. Alfonzo

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Editing of tRNAs is widespread in nature and either changes the decoding properties or restores the folding of a tRNA. Unlike the phylogenetically disperse adenosine (A) to inosine (I) editing, cytosine (C) to uridine (U) editing has only been previously described in organellar tRNAs. We have shown that cytoplasmic tRNA^Thr(AGU) undergoes two distinct editing events in the anticodon loop: C to U and A to I. In vivo, every inosine-containing tRNA^Thr is also C to U edited at position 32. In vitro, C to U editing stimulates conversion of A to I at the wobble base. Although …

Differential Effects Of Sodium And Magnesium Sulfate On Water Consumption By Beef Cattle, A. S. Grout, D. M. Veira, D. M. Weary, M. A. G. Von Keyserlingk, D. Fraser

Biochemistry Collection

The existing guidelines for maximum sulfate (SO₄) in cattle drinking water are based on Na2SO₄, although many water sources contain greater concentrations of MgSO₄. Two experiments compared the effect of different SO₄ salts on water consumption and fecal DM of cattle. In Exp. 1, 8 yearling heifers (initial BW = 345 ± 8 kg; mean ± SD) were watered twice daily with tapwater or water containing Na₂SO₄ or MgSO₄ at target levels of 1,500, 3,000, or 4,500 mg of SO₄/L for 2-d treatment periods separated by 2 …

Sequential Processing Of A Mitochondrial Tandem Protein: Insights Into Protein Import In Schizosaccharomyces Pombe, Oleh Khalimonchuk, Martin Ott, Soledad Funes, Kai Ostermann, Gerhard Rödel, Johannes M. Herrmann

Department of Biochemistry: Faculty Publications

The sequencing of the genome of Schizosaccharomyces pombe revealed the presence of a number of genes encoding tandem proteins, some of which are mitochondrial components. One of these proteins (pre-Rsm22- Cox11) consists of a fusion of Rsm22, a component of the mitochondrial ribosome, and Cox11, a factor required for copper insertion into cytochrome oxidase. Since in Saccharomyces cerevisiae, Cox11 is physically attached to the mitochondrial ribosome, it was suggested that the tandem organization of Rsm22-Cox11 is used to covalently tie the mitochondrial ribosome to Cox11 in S. pombe. We report here that pre-Rsm22-Cox11 is matured in two subsequent …

Purification And Initial Biochemical Characterization Of Atp:Cob(I)Alamin Adenosyltransferase (Eutt) Enzyme Of Salmonella Enterica, Nicole R. Baun, Jorge C. Escalante-Semerena

Department of Biochemistry: Faculty Publications

ATP:cob(I)alamin adenosyltransferase (EutT) of Salmonella

enterica was overproduced and enriched to ~70% homogeneity,

and its basic kinetic parameters were determined. Abundant

amounts of EutT protein were produced, but all of it remained

insoluble. Soluble active EutT protein (~70% homogeneous) was

obtained after treatment with detergent. Under conditions in which

cobalamin (Cbl) was saturating, _Km(ATP) = 10 µM, k_cat = 0.03 s^-1,

and V_max = 54.5 nM min^-1. Similarly, under conditions in which

MgATPwas saturating,K_m(Cbl) = 4.1µM, k_cat = 0.06 s^-1, andV_max= …