Iron Metabolism Inorganic Biochemistry and Regulatory Mechanisms 3-527-29653-0

Table of contents :
Iron Metabolism......Page 2
Contents......Page 18
1.1 Introduction......Page 35
1.2 Summary of heme biosynthetic pathways......Page 37
1.3 Mediators of iron-dependent regulation of iron metabolism......Page 39
1.4 Regulation of heme synthesis by iron......Page 41
2.1 Introduction: 5-aminolevulinate synthase and iron......Page 49
2.2.1 Isolation, purification and identification of the PLP cofactor......Page 52
2.2.2 Steady-state kinetics and mechanism of ALAS......Page 53
2.3.1 Identification of the Schiff base linkage between PLP and lysine-313......Page 55
2.3.2 Role of a glycine-rich loop as a PLP cofactor-binding site......Page 56
2.3.3 Role of aspartate-279 in enhancing the function of PLP and in ALAS catalysis......Page 58
2.3.5 Role of arginine-439 in substrate binding......Page 61
2.4 Conclusions......Page 63
3.1 Introduction......Page 69
3.2 Identification, purification and characterization of ferrochelatase......Page 70
3.3 Steady-state kinetic properties of ferrochelatase......Page 71
3.3.1 Ferrochelatase reaction mechanism......Page 72
3.3.2 Reducing conditions are not essential for ferrochelatase activity......Page 73
3.3.3 Site-directed mutagenesis......Page 75
3.3.4 Iron-substrate ligands as determined by Mossbauer spectroscopy......Page 76
3.4 The [2Fe-2S] cluster of mammalian ferrochelatases......Page 77
3.4.1 Conserved cysteines and iron-sulfur cluster binding......Page 78
3.5 The three-dimensional structure of Bacillus subtilis ferrochelatase......Page 79
3.6 Conclusions......Page 80
4.1 Introduction......Page 85
4.2 Iron transport in Saccharomyces cerevisiae......Page 86
4.2.2 Identification of FET3......Page 87
4.2.3 Fet3p is a multicopper oxidase......Page 88
4.2.4 Fet3p acts as a ferroxidase to mediate iron transport......Page 92
4.3 Oxidase-permease based iron transport systems in other species......Page 93
5.1 Introduction......Page 99
5.2.1 Structure......Page 103
5.3.1 Liver......Page 105
5.3.2 Barrier tissues......Page 107
5.4.1 Target tissues......Page 109
5.4.2.1 Interactions between the hemopexin and transferrin systems......Page 110
5.5.1 Protective role of hemopexin......Page 112
5.5.2 Increased oxidation state......Page 114
5.5.3.1 Redox sensitive......Page 115
5.5.3.2 For metallothionein regulation......Page 116
5.5.6.1 Role of copper in certain of the cellular and regulatory effects of hemopexin: intracellular oxidation state......Page 119
5.5.6.2 Nuclear translocation of transcription factors......Page 120
5.6 Conclusions......Page 122
6.2 Biochemical characteristics of cytochrome c peroxidase......Page 129
6.2.1 Amino acid sequence......Page 130
6.2.2 Three-dimensional structure of P.aeruginosa CCP and proposal for the P. denitrificans three-dimensional structure......Page 131
6.2.3 Calcium and its role in the activation mechanism......Page 132
6.3.1 UV/visible spectroscopy and activation of P.denitrificans CCP......Page 135
6.3.2 NMR spectra of oxidized and half-reduced CCP in the presence and absence of calcium......Page 138
6.3.3 EPR and Mossbauer studies......Page 140
6.4 Electrochemical measurements......Page 141
6.6 Conclusions......Page 148
7.2 The accessibility of the hemes of cytochrome c peroxidase......Page 151
7.3 The heme edge and the molecular surface of cytochrome c550......Page 152
7.4 Does cytochrome c550 bind as a dimer or as a monomer?......Page 154
7.5 What is the site of binding of cytochrome C550 on the cytochrome c peroxidase?......Page 157
7.6 How close is the approach of the heme group of the probe cytochrome to the hemes of the peroxidase?......Page 160
7.7 Conclusion......Page 163
8.1 The need for a balanced iron supply in cells......Page 165
8.2 Dietary iron absorption in mammals......Page 166
8.3 Coordinate control of cellular iron homeostasis is posttranscriptional and involves iron responsive elements (IREs) ......Page 167
8.4 Mechanisms for regulation of mRNA translation and stability by IRE/IRP interactions......Page 170
8.5 Fe-S centers as genetic switches: iron regulatory protein-1 (IRP1)......Page 171
8.6 Iron regulatory protein-2 (IRP2): closely related but different......Page 174
8.7 Regulation of IRPl and IRP2 by nitric oxide (NO)......Page 175
8.9 Is the Fe-S cluster of IRPl sensitive to oxidants?......Page 176
8.1 1 A model for the ‘delayed’ Fe-S cluster switch......Page 178
8.13 Physiological implications of IRP1 regulation by oxidative stress......Page 179
9.2 Studies of the purified protein......Page 187
9.3 Studies of E. coli cells......Page 190
9.4 Conclusions......Page 193
10.1 Introduction......Page 195
10.2 The complexity of the anaerobic ribonucleotide reductase......Page 196
10.3 Activity depends on the presence of a glycyl radical on the large component......Page 197
10.4 The small protein contains a unique iron-sulfur center......Page 199
10.5 Reduction of AdoMet by the reduced Fe-S center and formation of the glycyl radical......Page 203
10.6 A radical mechanism in class III RNRs......Page 205
10.7 A whole class of AdoMet-dependent metalloenzymes......Page 206
10.8 Conclusion......Page 207
11.2 Oxidative Stress Responses in Bacteria......Page 211
11.2.1 The oxyR system of E. coli and S. typhimurium......Page 212
11.2.2 The E.coli soxRS regulon......Page 213
1 1.3 NO-inducible gene expression in mammalian cells......Page 214
1 1.3.1 A complex response to NO in human cells......Page 215
11.3.2 Adaptive resistance to NO in motor neurons......Page 216
1 1.4 Summary and perspectives......Page 217
12.2 Ferritin gene regulation I (DNA - plants)......Page 221
12.3 Ferritin gene regulation II (mRNA - animals): iso-IRES and iso-IREs......Page 222
12.3.1 Constant features of IRES and IRPs......Page 224
12.3.2.1 Differential iso-IRP (IRP1 and IRP2) binding and variation at the IRE mid-helix distortion......Page 226
12.3.2.2 pH dependence of the internal loop/bulge conformation......Page 227
12.4.1 Variable features of ferroxidation and translocation......Page 228
12.4.2 Constant features of iron mineralization and release......Page 229
12.5 Conclusions......Page 230
13.2 Iron recycling and the evolution of the transport of oxygen......Page 233
13.4 The unlikely chance of iron overload and some conditions that can provoke it......Page 235
13.4.2 Hereditary Hemochromatosis (HH): a role for the immunological system in the regulation of iron overload......Page 236
13.5 Mechanisms......Page 239
13.6.1 The normal situation......Page 240
13.7 ‘But how?’......Page 241
13.8 Caveat......Page 242
14.1.1 Ferritins and bacterioferritin......Page 245
14.1.2 The Fe-uptake regulatory protein......Page 247
14.2 Effect of Cu2+ on the oxidative uptake of Fe2+ by E. coli bacterioferritin......Page 249
14.3 Engineering catalytically active dimeric R capsulatus bacterioferritin......Page 250
14.3.2 Characterization of the E128R/E135R mutant Bfr......Page 252
14.3.3 Interaction of the E128R/E135R mutant Bfr with Fe2+......Page 253
14.4 Heme binding to P. aeruginosa Fur......Page 254
14.5 Heme binding to Fur and Bfr......Page 256
14.6 Binding of metal ions to Fur and Bfr......Page 257
14.7 Catalytically active dimeric Bfr......Page 258
15.2.1 Conservation of dinuclear metal centers in ferritins......Page 261
15.2.3 Comparisons of dinuclear iron centers in ferritins and other proteins......Page 267
15.3.1 Ferroxidase activity of the dinuclear centers in ‘H-type’ ferritins......Page 268
15.3.2 Mechanism of Fe( II) oxidation at diiron centers in HuHF......Page 269
15.3.4 Stoichiometry of Fe( II) oxidation......Page 270
15.3.5 A third iron site in EcFtna......Page 271
15.3.6 Formation of blue or purple species as early oxidation products......Page 272
15.3.7 Are there alternative Fe(II) oxidation sites on ferritin molecules?......Page 275
15.3.8 Formation of oxo-bridged Fe(III) dimers......Page 276
15.4.1 Movement of iron from diiron centers and the formation of the iron-core......Page 277
15.4.2 Are the dinuclear centers repeatedly utilized for Fe(II) oxidation?......Page 278
15.5 In conclusion......Page 282
16.1 Introduction......Page 287
16.2 Methane monooxygenase......Page 288
16.3 Ribonucleotide reductase......Page 290
16.4 Ferritin......Page 292
16.5.1 Intermediate Hperoxo in MMOH......Page 293
16.5.2 Intermediate R2peroxo in D84E-R2......Page 296
16.6.1 Intermediate X in R2......Page 297
16.6.3 Intermediate X’ in W48F-R2......Page 300
16.7 Mechanistic considerations......Page 302
17.1 Signal transduction via protein phosphorylation......Page 309
17.2 Metallophosphatases: classification......Page 310
17.3 Metallophosphatase active site architecture......Page 312
17.4 Metal ion requirements and regulation by redox......Page 316
17.5 Calcineurin redox: implications for catalysis......Page 321
17.6 Site-directed mutagenesis: implications for catalysis......Page 325
17.7 Calcineurin redox: implications for in uiuo regulation......Page 329
18.1 Introduction......Page 337
18.2 Cytochrome P450 and soluble methane monooxygenase: components and general enzyme characteristics......Page 338
18.3 The catalytic reaction cycles......Page 340
18.4 Dioxygen activation......Page 342
18.5 Hydrocarbon oxidation......Page 346
18.6 Concluding remarks......Page 352
19.1 Introduction......Page 357
19.2 Components......Page 358
19.3 Intermediates......Page 359
19.4 Mechanism......Page 363
19.5 Regulation......Page 368
19.6 Conclusion......Page 370
20.2 The rubredoxin type centers......Page 375
20.3 Structural comparison of rubredoxin and desulforedoxin......Page 378
20.4 Single-metal replacement data in rubredoxin and desulforedoxin and crystal structures......Page 382
20.5.1 Desulfofenodoxin......Page 386
20.5.2 Rubrerythrin......Page 388
20.6 Conclusions......Page 389
21.1 Introduction......Page 393
21.2 Apo-DtxR crystal structure......Page 394
21.3 Metal-ion activation......Page 396
21.4 Mechanism of metal-ion activation......Page 397
21.5 Nucleic acid recognition......Page 399
21.6 DtxR homologs......Page 402
21.7 Conclusions......Page 403
Index......Page 407