Temperature dependence of NO binding modes in human neuroglobin

✍ Scribed by Florin Trandafir; Sabine Van Doorslaer; Sylvia Dewilde; Luc Moens

• Book ID: 104003339
• Publisher: Elsevier Science
• Year: 2004
• Tongue: English
• Weight: 213 KB
• Volume: 1702
• Category: Article
• ISSN: 1570-9639
• DOI: 10.1016/j.bbapap.2004.08.004

✦ Synopsis

Both the ferrous and ferric forms of wild-type neuroglobin are found to be hexacoordinated with axial ligation of the F8-His and E7-His. Rapidly growing Escherichia coli cell cultures with low O 2 concentration generate nitric oxide (NO). Combined electron paramagnetic resonance (EPR) and optical measurements show that wild-type human recombinant neuroglobin, overexpressed in such E. coli cells, still favors the F8His-Fe 2+ -E7His conformation, whereby only a small fraction of the protein binds NO. Upon mutation of the E7-His to Leu and Gln, the competition with the distal histidine disappears and the nitrosyl ferrous form is readily observed. At low temperature, the EPR spectra of the NO-ligated Ngb proteins consist of contributions from two geometrically different NO-heme conformations. In combination with EPR data of vertebrate hemoglobins and myoglobins, the temperature dependence of the EPR spectra of the NO adducts of ferrous hNgb and its E7-mutants proves a strong stabilization of one isomer by the E7-histidine in wt hNgb. It is shown that this is not related to the polarity of histidine, but to its specific binding characteristics.