Copper(II) protoporphyrin IX as a reporter group for the heme environment in myoglobin

Abstract

Copper(II) protoporphyrin IX has been introduced into apomyoglobin, and its utility as a reporter group of the heme environment has been examined. The Soret and visible absorption bands and electron spin resonance spectrum show that the Cu(II) is five coordinate, probably through coordination to the F-8 proximal histidine. The resonance Raman spectrum does not indicate any appreciable distortion from the solution conformation of copper(II) protoporphyrin IX dimethyl ester in CS2. The ultraviolet circular dichroism shows no alteration of the helical content of the globin from that of metmyoglobin. The circular dichroism of the porphyrin transitions suggests that the packing of the amino acid side chains around the porphyrin is different than that in the native metmyoglobin.

Binding Specificity of the Porphyromonas gingivalis Heme and Hemoglobin Receptor HmuR, Gingipain K, and Gingipain R1 for Heme, Porphyrins, and Metalloporphyrins

“…These were bound approximately four times more tightly than PPIX itself. All three metals that we examined in this study (iron, copper, and zinc) can bind to the histidine within the active site in heme-proteins (1,47,55). The observation that these metalloprotoporphyrins bind to HmuR somewhat better than PPIX itself is consistent with a histidine in HmuR serving as the axial ligand, which binds to the metal ion present in the porphyrin ring.…”

Resonance Raman spectroscopic studies in copper reconstituted and hybrid hemoglobins: Probe into subunit heterogeneity

“…This band ( 4 ) is well known as the -charge density marker band of iron porphyrins, heme proteins, metalloporphyrins, and metal reconstituted hemoglobins. 16,20,22,24,29 A comparison of the high frequency Raman spectrum of CuHb at both 413.1-and 406.7-nm excitation wavelengths indicate that the core and oxidation state marker bands are consistent with the earlier reported 4-and 5-coordinate porphyrin systems. 16,24,29 Note here that the 4-and 5-coordinate Raman marker bands in CuHb are not clearly separated out as in the case of NiHb.…”

“…16,20,22,24,29 A comparison of the high frequency Raman spectrum of CuHb at both 413.1-and 406.7-nm excitation wavelengths indicate that the core and oxidation state marker bands are consistent with the earlier reported 4-and 5-coordinate porphyrin systems. 16,24,29 Note here that the 4-and 5-coordinate Raman marker bands in CuHb are not clearly separated out as in the case of NiHb. 16 This becomes obvious because even in the 4-and 5-coordinate model Cu porphyrins 24 these bands are indistinguishable with respect to their position.…”

“…Figure 1(a,b) shows the high frequency RR spectra of CuHb at 413.1-and 406.7-nm excitation wavelengths, respectively. The oxidation and core size marker bands ( 4 , 3 , 2 , and 10 ) are consistent with the model 4-and 5-coordinate copper porphyrins 16,24,29 (Table I). An interesting feature is the appearance of an additional 10 band at 1640 cm Ϫ1 that is exclusively present at 406.7-nm excitation and absent at 413.1-nm excitation.…”

Resonance Raman characterization of cationic Co(II) and Co(III) tetrakis(N‐methyl‐4‐pyridinyl)porphyrins in aqueous and non‐aqueous media

“…At high pH we observed a red shift (7 nm) of the Soret band maximum of Co II P relative to its position in neutral aqueous solution. This may be due to coordination of cobalt by OH groups, since upon axial ligation of the porphyrin center metal by electronegative groups a pronounced red shift of the Soret band would be expected, 64,65 i.e. a 10 nm shift was observed for the cobalt derivative of TMpyP (4) in aqueous solution with an excess of ethoxide, 31 and also an 8 nm red shift occurred upon formation of Co III P(OH) 2 (see inset in Fig.…”