Ligand Binding and Protein Function Properties of the Thermobifida fusca truncated hemoglobin: the importance of the distal tyrosine residues

NICOLETTI, FRANCESCO P.; DROGHETTI, ENRICA; BUSTAMANTE, JUAN PABLO; HOWES, BARRY D.; FEIS, ALESSANDRO; ESTRIN, DARÍO; BOFFI, ALBERTO; SMULEVICH, GIULIETTA

Congreso; 18th International Conference on Oxygen-Binding and Sensing Proteins; 2014

As other bacterial truncated hemoglobins, hemoglobin from Thermobifida fusca displays genuine peroxidase activity (1). The polarity of the Tf-trHb distal cavity, characterized by the presence of TrpG8, TyrCD1, and TyrB10, is intermediate between that of vertebrate hemoglobins and heme-containing peroxidases. The role of these residues has been recently addressed by studying their interaction with different exogenous ligands [CO, F-, and HS-]. We found that only the anionic ligands OH- and F- establish three H-bonds with TrpG8, TyrCD1 and with a water molecule H-bonded to TyrB10 (6 and unpublished data), while the other ligands are stabilized by TrpG8 and TyrCD1 only. Since the OH- ligand is able either to accept or donate the proton, in the present work the results will be discussed in terms of the different capability of the TyrB10 and TyrCD1 residues to act as hydrogen bond donor or acceptor, and therefore, their possible roles in the peroxidase activity.