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Mech Toxic Action

by: Christelle Krajcik III

Mech Toxic Action ETX 214

Christelle Krajcik III
GPA 3.55


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This 18 page Class Notes was uploaded by Christelle Krajcik III on Wednesday September 9, 2015. The Class Notes belongs to ETX 214 at University of California - Davis taught by Staff in Fall. Since its upload, it has received 59 views. For similar materials see /class/191964/etx-214-university-of-california-davis in Environmental Toxicology at University of California - Davis.

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Date Created: 09/09/15
Matthew Wood ETX 214 So let s talk mechanisms April 26 2006 Suggested Reading 1 Free Radicals In Biology and Medicine Barry Halliwell amp John MC Gutteridge 2 Molecular Toxicology P David Josephy 3 An ioxidant and Redox Regulation of Genes CK Sen H Seis amp PA Baeuerle 02 as a toxic gas l EMlBALS Where did 02 come from O2 usage Xanthine oxidase Cytochrome P450 Disulfide oxidases ER Proline hydroxlase Lysine hydroxlase Disulfide Oxidases Ero1 amp Evr1 S s s gt SH 54 575 5 5 sis EN 575 57 er 7 l 2me Mann mum Malacular cell 5mm O2 toxicity in E coli r mil a Clol n molecules ix 10 397 pa Cultural absorlmncc 4500mm u Fumarase FeS Fumarase A unstable Fumarase B How to organisms sense changes in 02 levels What needs to change in an organism for adaptation to low or high 02 level O2 sensing in Human Hypoxia Hypoxiainducible factor HIF interacts with hypoxia response element in the Erythropoietin gene EPO shown to regulate the expression of 100 genes HIF protein stability regulated by 02 levels O2 sensing in Human HypoxiaHIF What is a Free Radical Definition a free radical is any species capable of independent existence that contains one or more unpaired electrons What are Reactive Oxygen Species ROS Table 14 Reactive oxygen specie Radicals Nonerndicnls Supernxidu 05 Hydrogen peroxide H302 Hydroxyl H39 Hypochlorous ICld HOCIquot I cruxyl R03 Ozone O Alkoxyi RO39 Singlet oxygen Ag Hydropcroxyl H03 I cmxynimta NLO quotCould equally well be called a reamvc chlnmmting pcucs39v Where do ROS come from Xanthine oxidase Cytochrome P450 Disulfide oxidases ER Proline hydroxylase Lysine hyd roxylase ROS generation in vivo SN 5 an 5 345mm 5mm Ze H 5 w r Ze 2 Ewl EM if 71 I I MM Nalum Reviews Molecular Cell Einlogy How much 0239 is made in the human body Typical adult uses 35 ml Ozlkgmin or 147 molday lfjust 1 of consumed 02 makes 0239 then 17 kgyear E coli produce 5 M 0239 per second What makes ROS so reactive Redox Potentials AG AH TAS Negative AG spontaneous reaction AG nFAE Positive AE spontaneous reaction 0 Am ne Ared E A Bred he Box EOB on Bred Ared Box AEO EOA 39 EOB acceptor mum Cellular Redox Example sis xt k 6556 Z Aux zasu ll S x L Arm PlSet Km z m i all it l t 1 It ROS Redox Potentials half reaction OH e39 H gtHZO SPONTANEOU Very OXIdIZIng The Hydroxyl Radical H202 Fe Fe OH39 second order rate constant k2 76 M391s391 note Copper Cu2 can also react with H202 UV HOOH gt Hydroxyl radical in vivo Why second order rate constant k2with biomolecules Compound pH Rate constant M 1s 1 Adenosine 74 25 x 109 Guanine 10 x1010 Histidine 67 30 X 109 Ribose 7 12 x109 Plasma Albumin gt 1010 At the diffusion limit ROS damage in vivo proteins nucleic acids lipids cnzsozn 39 m 1 ohmic n W gquot When can ROS damage can be useful The PerR transcription factor senses H202 by metalcatalysed histidine oxidation Nature March 2006 JinWon Lee amp John Helmann Department of Microbiology Cornell PerR Transcription repressorfrom B subtilis PerR is a dimer amp related to the Fur repressor Presence of ROS gt10 mM inactivates PerR H202 regulate the expression of antioxidant genes binds one Fe2 or Mn2 and one Zn2 in 44202 0 p o a 100 E 10 Gene reported 3 1 assay I gaffwwa evade 6 PerR oxidation by Fe2 Fe2 oxidizes PerR a s soil N ED mmzaiion Purng mm W 17 was we 151424 Reiulive Inuiecuiar mass b Znquot39nrMn7 uM 1 10 too 10 mo 4 4 iorMFEZ Z 39 M iM 7109 n m v OXIdlzed PerR 04 0 cannot bind DNA 39i 3 4 5 8 ii c eauiasewma u 00mm i i 0 mm m 9 7 r a 1 v i Catalase inhibits Fe2 induced oxidation of PerR eaiaiaseiu mw PerR is oxidized on key Histidine residues in vivo wn Luvo Ho 39 n o i i i 2m 2sz ma mo 54 u m A i H V a emquot Next Defense against oxidative stress Oxidative Stress Perception Signal Transduction amp Gene Regulation lm WWWenvtuxucdaviseduWnndLabElXZMUXZM him Matthew vvuuu May 12qu Oxidative Stress Concepts 1 Wnere do ROS come from 2 Free radicals vs ROS 3 Redox potential AE and ROS reactions 4 Wnat is an antioxidant 5 Wnat types of genesproteins are involved in ROS defense Aerobic life the undisciplined reduction of O2 mm mudmcatmn u pvmems Othenypes uvpymem umauun mmmm femuamvh 7mm u lye1mm MM 7mm Huw pveva em ave msumue band m a new 12 msumde 2H7 Huw pveva em a band m a Huw pveva em ave msumde band m a new Anuumam enzymes m expusuve suu Mvmmasedm s whuvan m m m anaemb c mm m embmvmmh Fndamch a 3 Dubs mmmm m mm as mum mm Ames Lab circa early 1980 s How are these responses regulated Adaptive response to H202 Dvetrealed o H E 39 not pretreated 5 7 p su sated chloramnhenicol 2 4D so Mlnutes anev 1mm H702 Challenge Christman etal Cell 41 753762 1985 Increased protein expression after H202 treatment Christman etal Cell 41 753762 1985 Isolated mutants that were resistant to H202 Wild Typ 9 MW RD Christman etal Cell 41 753762 1985 Isolated mutants that were resistant to H202 mm 2 Eruyme Animus Elevated m mm 7 Minimal blucnse LB EMymL Assaycd 112 mm mm mmuun L72 may Fold luminlon cm llse Wham Culls n M 20 65 A An in Cell Enact 22 in 5a 28 A50 i7 Sun v xlde Dismma a Manganese 5 22 239 1o l5 Is in n n a 0 NA 0 s o a o s elutatmcna Reduclase CnilFxlmcl Mg m an ma 093 m Akylnydmpuwkidv Rommasn Whole Calls 0 was u 72 an cows 0 036 5 a Call Extmu ND ND ND n 22 o as a o Christman etal Cell 41 753762 1985 What is OxyR Prokaryotic Gene Expression Positive Regulation Transcription IIM No Activator Negative Regulation Nu X ATrznscrip nn Promoter Operator 77 Transcription Nu 7 Transcription No Repressor OxyR the transcription factor mrJ 5 5 F ms Jigcgy 00 ms 390 as s 5 ass Tn insertions I 234 5 pBJM003 39 mm EDIDRI EcoRlEle 5am I W4 In 4 pAOIG I Sequence homology to prokaryo ic transcriptional activators Christman et al PNAS 86 3484 1989 OxyR Direct activation by 02 A a eii DW 07 7 0M 0 2 2 zoovaoww i no i m i m I mum D7 07 N7 N2 innquot ug i 397 39 O D W 000 no5 0009 Wm WM i231567 izii G Storz et al Science 1990 248 189194 OxyR oxidized and reduced cause differential DNA binding u u mu IIIIll III Redox Regulationquot Toledano et al Cal1994 78 879 Sequence Homology of OxyR 807305 actswide myin rurala EUWYUS rhinchia my 305 aa Mima viroluvari anlhamvnas campesms r seudamanas aemgmosa OxyR H202 causes disquide bond formation we 4 r c fmdnoed B m 3 o a a 2 3 n z ymCsA vaC 998 xyFiOEDBS 5 o o a woman omomun a women n momma uM H202 Zheng et al Science 1998 279 1718 OxyR Protein Structure no trangcriptional transqriptional activation activation Choi et al Cal2001 105 10313


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