Haem-apoprotein interactions detected by resonance Raman scattering in Mb- and Hb-derivates lacking the saltbridge His146 beta-Asp94 beta.
The dispersion of the depolarization ratio of oxidation- and spin-marker lines of sperm whale myoglobin derivatives (oxyMb, deoxyMb, ferric Mb-CN) and of ferric Hb-CN have been measured for different pH-values in the acid and alkaline region. No pH-dependence in the region above pH = 6.5 has been found. Below pH = 6.5, however, a significant pH-dependence of the oxyMb-oxidation marker line at 1,375 cm-1 exists. Additionally, a weak pH-dependence of the corresponding 1,355 cm-1 line of the deoxymyoglobin spectrum is observed. This effect can be explained assuming a titration of distal histidine, inducing a rupture of the ligand-imidazole H-bond in the case of oxymyoglobin. The pH-independent depolarization ratio disperson above pH = 6.5 in all systems investigated is explained by the lack of the haemoglobin saltbridge between His(HC3) beta and Asp(FG5) beta, which is essential for the cooperativity in the haemoglobin system.
D000818:Animals; D001059:Apoproteins / Q000378:metabolism; D001224:Aspartic Acid; D006418:Heme / Q000378:metabolism*; D006454:Hemoglobins / Q000378:metabolism*; D006639:Histidine; D006863:Hydrogen-Ion Concentration; D009211:Myoglobin / Q000378:metabolism*; D013059:Spectrum Analysis, Raman; D013329:Structure-Activity Relationship; D014907:Whales
D001059:Apoproteins; D006454:Hemoglobins; D009211:Myoglobin; D001224:Aspartic Acid; D006418:Heme; D006639:Histidine