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1.
J Biol Inorg Chem ; 16(6): 869-80, 2011 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-21547575

RESUMO

DNA-binding proteins from starved cells (Dps) differ in the number and position of charged residues along the "ferritin-like" pores that are used by iron to reach the ferroxidase center and the protein cavity. These differences are shown to affect significantly the electrostatic potential at the pores, which determines the extent of cooperativity in the iron uptake kinetics and thereby the mass distribution of the ferric hydroxide micelles inside the protein cavity. These conclusions are of biotechnological value in the preparation of protein-enclosed nanomaterials and are expected to apply also to ferritins. They were reached after characterization of the Dps from Listeria innocua, Helicobacter pylori, Thermosynechococcus elongatus, Escherichia coli, and Mycobacterium smegmatis. The characterization comprised the calculation of the electrostatic potential at the pores, determination of the iron uptake kinetics in the presence of molecular oxygen or hydrogen peroxide, and analysis of the proteins by means of the sedimentation velocity after iron incorporation.


Assuntos
Proteínas de Bactérias/química , Proteínas de Ligação a DNA/química , Ferritinas/química , Ferro/química , Peróxido de Hidrogênio/química , Modelos Moleculares , Dados de Sequência Molecular , Oxidantes/química , Oxirredução , Oxigênio/química , Conformação Proteica , Eletricidade Estática
2.
Extremophiles ; 15(3): 431-9, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-21487935

RESUMO

Ferritin from the hyperthermophilic anaerobe Thermotoga maritima, a bacterium of ancient phylogenetic origin, is structurally similar to known bacterial and eukaryotic ferritins: 24 identical subunits assemble into a shell having octahedral symmetry and a Mr of about 460 kDa. T. maritima ferritin (TmFtn), purified to homogeneity as a recombinant protein, contains approximately 2-3 iron atoms and can incorporate efficiently up to 3,500 atoms in the form of a ferric oxy-hydroxide mineral at 80°C, the optimal growth temperature of the bacterium. The 24-mer unexpectedly dissociates reversibly into dimers at low ionic strengths. In turn, dimers re-associate into the native 24-mer assembly at high protein concentrations and upon incorporation of iron micelles containing at least 500 Fe(III). TmFtn uses O(2) as efficient iron oxidant. The reaction stoichiometry is 3-4 O(2):Fe(II) as in all bacterial ferritins. Accordingly no H(2)O(2) is released into solution, a feature reflected in the in vitro ability of TmFtn to reduce significantly iron-mediated oxidative damage to DNA at 80°C. A similar TmFtn-mediated ROS detoxifying role likely occurs in the bacterium which lacks the SOD/catalase defense systems of the aerobic world.


Assuntos
Proteínas de Bactérias/metabolismo , Dano ao DNA , DNA Bacteriano/metabolismo , Ferritinas/metabolismo , Ferro/metabolismo , Estresse Oxidativo , Thermotoga maritima/metabolismo , Sequência de Aminoácidos , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Clonagem Molecular , Cristalografia por Raios X , Ferritinas/química , Ferritinas/genética , Temperatura Alta , Modelos Moleculares , Dados de Sequência Molecular , Concentração Osmolar , Oxirredução , Estabilidade Proteica , Estrutura Quaternária de Proteína , Subunidades Proteicas , Espécies Reativas de Oxigênio/metabolismo , Proteínas Recombinantes/metabolismo , Thermotoga maritima/genética
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