B12 METABOLISM IN HUMANS By NICOLE AURORA LEAL A ...

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118 B Figure 4-3. Immunogold localization of the PduP enzyme. A, Wild-type S. enterica; B, strain BE191 (∆pduP). The 12 nm gold particles (small black circles) indicate the location of the PduP protein. The arrows point to the polyhedral bodies. Bars 100 nm
CHAPTER 5 CONCLUSIONS In humans, cobalamin cofactors are required coenzymes for two enzymatic reactions that are vital to human health. These coenzymes are used in propionate metabolism and methionine biosynthesis, and in humans, deficiencies in cobalamin metabolism result in methylmalonic aciduria and homocystinuria. Nine complementation groups associated with such deficiencies have been identified. Historically, progress on understanding these diseases has been slow due to difficulties in purifying the enzymes involved as well as the lack of facile genetic methods. A bacterial model system was used to circumvent some of these problems and allowed progress on the identification and characterization of the genes and enzymes involved in these rare, but devastating disorders. Identification of the Bovine and Human Adenosyltransferase In Chapter 2, S. enterica was used as a model system for the identification of the bovine and human ATR cDNAs by complementation analysis. In this screening technique, the bovine cDNA was isolated by complementing an ATR deficient S. enterica strain. Subsequently, sequence similarity searches using the bovine ATR cDNA identified a homologous human gene. Both human and bovine expression libraries were screened; however, complementing clones were only found from the bovine library. This could have been due to the relative abundance of ATR mRNA in these systems. Ruminant livers have the highest reported concentration of <strong>B12</strong>-dependent 119
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B12 METABOLISM IN HUMANS By NICOLE
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The work in this dissertation is de
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TABLE OF CONTENTS Page ACKNOWLEDGME
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General Molecular and Protein Metho
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LIST OF TABLES Table page 1-1. Aden
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3-7. Stoichiometry of the MSR-ATR s
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DTT dithiothreitol E. coli Escheric
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Abstract of Dissertation Presented
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CHAPTER 1 INTRODUCTION History of C
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3 (DMB). The DMB moiety is covalent
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5 and deoxyadenosine. After hydroge
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7 homocysteine recycling and methio
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methylmalonic acid. Methylmalonic a
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folate-dependent reactions includin
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tetanomorphum, P. shermanii, Euglen
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enzyme. This suggests that cob(II)a
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at the 5’-C of ATP by cob(I)alami
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iochemical studies and complementat
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1997). Both cases of the cblD disor
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23 The cblB complementation group i
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(Watkins et al. 2002). Some patient
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Chapter 2 of this dissertation repo
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Corrin Ring Dimethyl benzimidazole
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Classes Eliminases Dehydratases OH
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A) B) CH 3THF 33 MS-cob(I)alamin Me
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propanol dehydrogenase (PduQ) propa
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or from mutations that impair the a
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1989). 5-bromo-4-chloro-3-indolyl-
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41 5’-GCCGCCGGTACCGATGACGACGACAAG
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43 Growth of Adenosyltransferase Ex
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anti-rabbit IgG (γ-chain specific)
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sequence similarity to a known ATR
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ATRs were produced as fusion protei
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51 of the lacI repressor (not shown
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in which proteins bind B12, the "ba
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libraries may be particularly usefu
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57 Figure 2-1. Multiple sequence al
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Table 2-2. Specific activities of b
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61 1 2 3 4 5 25 kDa Figure 2-4. Wes
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63 (cyanocobalamin, CNCbl) and hydr
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65 5’- triphosphate (ATP), and di
Page 83 and 84: extracts of ATR 239K (160 mg protei
Page 85 and 86: Milford, MA). Samples (200 µl) wer
Page 87 and 88: Linearity of the ATR reaction 71 Th
Page 89 and 90: 73 reactions was characteristic of
Page 91 and 92: 75 MSR Produces little Cob(I)alamin
Page 93 and 94: Johnson et al. 2001, Saridakis et a
Page 95 and 96: AdoCbl by the MSR-ATR system. Exper
Page 97 and 98: propionyl-CoA PCC (2S)-methylmalony
Page 99 and 100: kDa 97 66 45 31 21 14 7 83 1 2 3 4
Page 101 and 102: 85 Table 3-3. The MSR-ATR system se
Page 103 and 104: Absorbance 0.5 0.4 0.3 0.2 0.1 0.0
Page 105 and 106: Wavelength, (525 nm) 0.24 0.23 0.22
Page 107 and 108: Activity, (nmol min-1 Activity, (nm
Page 109 and 110: al. 1988). The aldehyde is then dis
Page 111 and 112: CoA-acylating propionaldehyde dehyd
Page 113 and 114: 97 previously published DNA sequenc
Page 115 and 116: mM CHES (2-[N-cyclohexylamino]ethan
Page 117 and 118: 101 For the conjugation step, strai
Page 119 and 120: 103 from New England Biolabs (Bever
Page 121 and 122: 105 Propionaldehyde Dehydrogenase A
Page 123 and 124: 107 fraction. Following centrifugat
Page 125 and 126: 109 antiserum obtained was specific
Page 127 and 128: 111 biochemical evidence was presen
Page 129 and 130: 113 Table 4-1. Bacterial strains Sp
Page 131 and 132: 115 Table 4-3. Propionaldehyde dehy
Page 133: kDa 209 80 49 35 29 117 1 2 3 4 Fig
Page 137 and 138: 121 substitutions that are common p
Page 139 and 140: 123 Studies also indicated that hum
Page 141 and 142: LIST OF REFERENCES Aberg, A., S. Ha
Page 143 and 144: 127 Bradford, M. 1976. A rapid and
Page 145 and 146: 129 Fenton, W. A. and L. E. Rosenbe
Page 147 and 148: 131 Johnson, C. L. V. J., E. Pechon
Page 149 and 150: 133 Mellman, I., H. F. Willard and
Page 151 and 152: 135 Rossi, M., J. P. Glusker, L. Ra
Page 153 and 154: 137 Vlasie, M., S. Chowdhury and R.
Page 155 and 156: BIOGRAPHICAL SKETCH Nicole Aurora L
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