Site-directed mutagenesis of bacterial hemoglobin: the role of glutamine (E7) in oxygen-binding in the distal heme pocket

Archives of Biochemistry and Biophysics
K L DikshitD A Webster

Abstract

The bacterial and yeast hemoglobins have a glutamine instead of histidine in the E7 position of the distal heme pocket. The recently determined crystal structure of Vitreoscilla hemoglobin (VHb) indicates that this residue is oriented out of the heme pocket and may not ligand the bound oxygen. This is in contrast to elephant myoglobin which also has a Gln(E7) but which does ligand the bound oxygen. This residue was changed in VHb using site-directed mutagenesis to leucine (VHbL) or to histidine (VHbH). Spectral and kinetic studies of the binding of oxygen and CO to VHbL showed that this substitution had little effect on the ligand-binding properties of this protein, evidence that Gln(E7) does not H-bond the bound ligand, in agreement with the findings of the crystallographic study of VHb. In contrast, the functional properties of VHbH were drastically altered in a way suggesting that the E7His may itself be liganded to the heme iron. These studies are further evidence that the distal heme pocket in VHb and related microbial hemoglobins differs from that in mammalian hemoglobins and may resemble in some ways the heme pocket in cytochrome b5.

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Citations

Sep 13, 2006·International Journal of Biological Sciences·Yaneenart SuwanwongVirapong Prachayasittikul
Dec 8, 2004·Biochemical and Biophysical Research Communications·Sandhya VermaDale A Webster
Mar 27, 2004·Biochemical and Biophysical Research Communications·Sang Yeol LeeDale A Webster
Jan 1, 2012·Computational and Structural Biotechnology Journal·Benjamin C StarkKrishna R Pagilla
Jan 13, 2015·Applied Microbiology and Biotechnology·Benjamin C StarkKanak L Dikshit
Jun 25, 2002·The Journal of Biological Chemistry·Kyung-Won ParkDale A Webster
Jul 5, 2001·The Journal of Biological Chemistry·A N HvitvedM S Hargrove
Mar 23, 2013·Acta Crystallographica. Section F, Structural Biology and Crystallization Communications·Sireesha RatakondaAndrew J Howard
Sep 12, 2020·Trends in Biotechnology·Xinrui ZhaoJian Chen

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