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Effects of pH on the activity and structure of choline oxidase from Alcaligenes species

100%

Hekmat A., Saboury A. A., Moosavi-Movahedi A. A., Ghourchian H., Ahmad F.

Acta Biochimica Polonica

2008

tom 55

nr 3

549-557

A reversible effect of pH on the ionization of amino-acid residues at the active center of choline oxidase was observed near the optimum pH (8). Inactivation of choline oxidase took place in the pH ranges 3–6 and 9–11, in which irreversible changes in the structure occur leading to the enzyme inactivation. The first order rate constants of the enzyme’s inactivation at various pH values were estimated for the irreversible changes. The Arrhenius analysis revealed no significant changes in the activation enthalpy, while an increase in the activation entropy reflected an increase in the conformational freedom.

15N magnetic relaxation study of backbone dynamics of the ribosome-associated cold shock response protein Yfia of Escherichia coli

67%

Zhukov I., Bayer P., Scholermann B., Ejchart A.

Acta Biochimica Polonica

2007

tom 54

nr 4

769-775

In the solution structure of the ribosome-associated cold shock response protein Yfia of Escherichia coli in the free state two structural segments can be distinguished: a well structured, rigid N-terminal part displaying a βαβββα topology and a flexible C-terminal tail comprising last 20 amino-acid residues. The backbone dynamics of Yfia protein was studied by 15N nuclear magnetic relaxation at three magnetic fields and analyzed using model-free approach. The over all diffusional tumbling of the N-terminal part is strongly anisotropic with a number of short stretches showing increased mobility either on a subnanosecond time scale, or a micro- to milli second time scale, or both. In contrast, the unstructured polypeptide chain of the C-terminal part, which cannot be regarded as a rigid structure, shows the predominance of fast local motions over slower ones, both becoming faster closer to the C-terminus.

Ograniczanie wyników

2 Acta Biochimica Polonica

1 Ahmad F.

1 Bayer P.

1 Ejchart A.

1 Ghourchian H.

1 Hekmat A.

1 Moosavi-Movahedi A. A.

1 Saboury A. A.

1 Scholermann B.

1 Zhukov I.

1 2008

1 2007

Wyniki wyszukiwania

Effects of pH on the activity and structure of choline oxidase from Alcaligenes species

15N magnetic relaxation study of backbone dynamics of the ribosome-associated cold shock response protein Yfia of Escherichia coli