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Pressure effects reveal that changes in the redox states of the heme iron complexes in the sensor domains of two heme‐based oxygen sensor proteins, Ec DOS and YddV, have profound effects on their flexibility
Author(s) -
Anzenbacher Pavel,
Marchal Stéphane,
Palacký Jan,
Anzenbacherová Eva,
Domaschke Thomas,
Lange Reinhard,
Shimizu Toru,
Kitanishi Kenichi,
Stranava Martin,
Stiborová Marie,
Martinkova Marketa
Publication year - 2014
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.13060
Subject(s) - heme , chemistry , redox , myoglobin , catalysis , stereochemistry , biophysics , enzyme , biochemistry , inorganic chemistry , biology
The catalytic activity of a heme‐based oxygen sensor phosphodiesterase from Escherichia coli ( Ec DOS ) towards cyclic di GMP is regulated by the redox state of the heme iron complex in the enzyme's sensing domain and the association of external ligands with the iron center. Specifically, the Fe( II ) complex is more active towards cyclic di GMP than the Fe( III ) complex, and its activity is further enhanced by O 2 or CO binding. In order to determine how the redox state and coordination of the heme iron atom regulate the catalytic activity of Ec DOS , we investigated the flexibility of its isolated N‐terminal heme‐binding domain ( Ec DOS ‐heme) by monitoring its spectral properties at various hydrostatic pressures. The most active form of the heme‐containing domain, i.e. the Fe( II )– CO complex, was found to be the least flexible. Conversely, the oxidized Fe( III ) forms of Ec DOS ‐heme and its mutants had relatively high flexibilities, which appeared to be linked to the low catalytic activity of the corresponding intact enzymes. These findings corroborate the suggestion, made on the basis of crystallographic data, that there is an inverse relationship between the flexibility of the heme‐containing domain of Ec DOS and its catalytic activity. The Fe( II )– CO form of the heme domain of a second heme‐based oxygen sensor, diguanylate cyclase (YddV), was also found to be quite rigid. Interestingly, the incorporation of a water molecule into the heme complex of YddV caused by mutation of the Leu65 residue reduced the flexibility of this heme domain. Conversely, mutation of the Tyr43 residue increased its flexibility.