Identification of the iron-carbonyl stretch in distal histidine mutants of carbonmonoxymyoglobin

Mechanism for Transduction of the Ligand-Binding Signal in Heme-Based Gas Sensory Proteins Revealed by Resonance Raman Spectroscopy

“…32 The ν Fe-CO frequency of CO-bound CooA is observed at 487 cm -1 , 33,34 which is similar to that observed for the H64L Mb mutant. 31 This suggests that the polarity of the distal side in CooA is comparable to that in the H64L Mb mutant ( Figure 2B). If Pro2, which appears to have a negative charge based on the frequency of ν 11 , 35 interacts with bound CO, the ν Fe-CO frequency of CooA would be significantly lower than that observed for the Mb H64L mutant.…”

“…31 In contrast, addition of a positive charge by replacing Val at position 68 with Asn (V68N) increases the ν Fe-CO frequency to 527 cm -1 . 32 The ν Fe-CO frequency of CO-bound CooA is observed at 487 cm -1 , 33,34 which is similar to that observed for the H64L Mb mutant.…”

“…the so-called distal His (His64) is present near CO, ν Fe-CO is observed at 508 cm -1 (Figure 2, WT), 29,31 whereas replacement of the distal His with Leu (H64L) decreases the ν Fe-CO frequency to 490 cm -1 . 31 In contrast, addition of a positive charge by replacing Val at position 68 with Asn (V68N) increases the ν Fe-CO frequency to 527 cm -1 .…”

CO as a vibrational probe of heme protein active sites

“…An extensive series of myoglobin variants with distal pocket mutations [2,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38], form the most comprehensive available set ot mFeC/mCO data (Table 1) at constant trans ligation; these data are plotted in Fig. 1 and form the canonical Mb line, against which other adducts can be compared.…”

Carbon Monoxide Complex of Cytochrome b5 at Acidic pH

“…The Fe-C and CO frequencies of CO-bound heme proteins reflect the electronic structure of the heme and its environment (10,18) The axial ligand and electrostatic fields of heme proteins have been shown to influence significantly the Fe-C and CO frequencies of the bound CO (15,16,26,27). For example, existence of positive charges from proton donating residues close to the bound CO causes the electron density of the * orbital of the bound CO to increase through the backbonding from the filled d orbital of the iron, which causes increase in the Fe-C frequency.…”