Oxygen and temperature-dependent structural and redox changes in a novel cytochrome c4 from the purple sulfur photosynthetic bacterium Thiocapsa roseopersicina

doi:10.1016/j.abb.2007.07.031

Archives of Biochemistry and Biophysics

Volume 467, Issue 2, 15 November 2007, Pages 174-184

https://doi.org/10.1016/j.abb.2007.07.031 Get rights and content

Abstract

A novel cytochrome c₄, the first of this type in purple phototrophic bacteria has been discovered in Thiocapsa roseopersicina. The fact that cytochrome c₄ has been found in an anaerobic organism puts in question the up hereto suggested role of cytochromes c₄ in the aerobic respiratory metabolism. The structure of cytochrome c₄ was studied under both aerobic and anaerobic conditions, using differential scanning calorimetry and a combination of redox potentiostatic measurements with CD and UV–Vis absorption techniques. Cytochrome c₄ maintained its functional capability at high temperature (60 °C) if it was kept under anaerobic conditions. With increasing temperature under aerobic conditions, however, there are dramatic conformational changes in the protein and coordination changes on the iron side. Presumably oxygen binds to the iron at the position left vacant by the methionine and facilitates conformational changes with low reversibility.

Section snippets

Experimental procedures

Thiocapsa roseopersicina was grown under standard photosynthetic conditions as described earlier [16]. Cells were harvested in the logarithmic phase of growth and were stored at −20 °C.

Molecular mass and heme content of cytochrome

We have purified and identified three cytochromes from T. roseopersicina: a flavocytochrome c with two subunits (22 and 42 kDa), which is probably the same as described earlier [33], and two cytochromes with only one peptide chain. We used the larger cytochrome monomer in this study which displayed only one band on SDS gradient PAGE, at a molecular mass of ∼25 kDa. Recently, we have determined the exact mass by mass spectrometry; 21582 Da [34]. This unit contains two hemes per molecule, as

Classification of the cytochrome c₄ from T. roseopersicina

Four different cytochromes have been purified and characterized from T. roseopersicina so far [33], [41], [42], [43]. The cytochrome c₄ presented in this paper is different from any of the previously purified ones.

Three of the reported cytochromes from T. roseopersicina have substantially higher (55 kDa [42] and 180 kDa [41]) or lower (4∗11 kDa [43]) molecular masses than that of cytochrome c₄. The flavocytochrome c₅₅₂ from T. roseopersicina[33] possesses a di-heme subunit with a similar mass (∼21

Acknowledgments

We are grateful for the financial support of the Hungarian Science Foundation [OTKA T049276 and OTKA T049207] and AUTOESKORT Ltd. Rui M.M. Branca acknowledges the financial support of the Portuguese Science and Technology Foundation under the PhD fellowship of POCTI, SFRH/BD/13128/2003.

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Oxygen and temperature-dependent structural and redox changes in a novel cytochrome c4 from the purple sulfur photosynthetic bacterium Thiocapsa roseopersicina

Abstract

Section snippets

Experimental procedures

Molecular mass and heme content of cytochrome

Classification of the cytochrome c4 from T. roseopersicina

Acknowledgments

FEBS Lett.

J. Mol. Biol.

Biochim. Biophys. Acta

J. Inorg. Biochem.

J. Biol. Chem.

Anal. Biochem.

Anal. Biochem.

Meth. Enzymol.

Arch. Biochem. Biophys.

Anal. Biochem.

Anal. Biochem.

Meth. Enzymol.

J. Photochem. Photobiol. B

J. Photochem. Photobiol. B

FEBS Lett.

Biochem. Biophys. Res. Commun.

Biochim. Biophys. Acta

Structure

Structure

Biochim. Biophys. Acta

J. Inorg. Biochem.

Biochem. J.

Biochem. J.

Biochim. Biophys. Acta

Eur. J. Biochem.

Biochem. J.

J. Biochem.

Biochemistry

Chem. Rev.

Oxygen and temperature-dependent structural and redox changes in a novel cytochrome c₄ from the purple sulfur photosynthetic bacterium Thiocapsa roseopersicina

Classification of the cytochrome c₄ from T. roseopersicina