Flavin and heme structures in lactate: cytochrome c oxidoreductase: a resonance Raman study

Abstract

Resonance Raman spectra of Hansenula anomala L-lactate:cytochrome c oxidoreductase (or flavocytochrome b2), of its cytochrome b2 core, and of a bis(imidazole) iron-protoporphyrin complex were obtained at the Soret preresonance from the oxidized and reduced forms. Raman contributions from both the isoalloxazine ring of flavin mononucleotide (FMN) and the heme b2 were observed in the spectra of oxidized flavocytochrome b2. Raman diagrams showing frequency differences of selected FMN modes between aqueous and proteic environments were drawn for various flavoproteins. These diagrams were closely similar for flavocytochrome b2 and for flavodoxins. This showed that the FMN structure must be very similar in both types of proteins, despite their very different proteic pockets. However, the electron density at this macrocycle was found to be higher in flavocytochrome b2 than in these electron transferases. No significant difference was observed between the heme structures in flavocytochrome b2 and in cytochrome b2 core. The porphyrin center-N(pyrrole) distances in the oxidized and reduced heme b2 were estimated to be 1.990 and 2.022 A from frequencies of porphyrin skeletal modes, respectively. The frequency of the vinyl stretching mode of protoporphyrin was found to be very affected in resonance Raman spectra of flavocytochrome b2 and of cytochrome b2 core (1634-1636 cm-1) relative to those observed in the spectra of iron-protoporphyrin [bis(imidazole)] complexes (1620 cm-1). These specificities were interpreted as reflecting a near coplanarity of the vinyl groups of heme b2 with the pyrrole rings to which they are attached. The low-frequency regions of resonance Raman indicated that the iron atoms of the four hemes b2 are in the porphyrin plane whatever their oxidation state. The histidine-Fe-histidine symmetric stretching mode was located at 205 cm-1 in the spectra of flavocytochrome b2 and of cytochrome b2 core. It was insensitive to the iron oxidation state and indicated strong Fe-His bonds in both states.

Electrostatic Control of the Isoalloxazine Environment in the Two-electron Reduced States of Yeast Glutathione Reductase

“…Our study shows frequencies close to those published in the study of Schmidt et al (24). With reference to the RR frequencies of FAD in water, Raman diagrams were previously drawn to visualize the apoprotein effect on the high frequency modes of the isoalloxazine ring (19,26). In the diagram of oxidized GR (Fig.…”

“…In the diagram of oxidized GR (Fig. 5), the frequency shifts detected for GR are generally negative, indicating an electron-deficient isoalloxazine ring (19,26). The shapes of the Raman diagrams were associated with the electron distribution through the three rings of the isoalloxazine moiety and correlated with the biological activities of several flavoproteins (19,26).…”

Study of the Coordination Chemistry of Prostaglandin G/H Synthase by Resonance Raman Spectroscopy

“…OH (492 cm-l; Asher and Schuster, 1979;Asher et al, 1977) and Mb Fe(II1) . OH (491 cin '; Asher and Schuster, 1979 ;Asher et al, 1977 ;Desbois et al, 1979) and slightly lower than the value (503 cm-') reported for the low-spin horseradish peroxidase Fe(II1) I OH complex (Sitter et al, 1988). Isotopic substitution of H,'"O by H2"0 does not allow discrimination between -OH, which should produce a shift from 489 cm-' to 469 cm ', and HZO, which should produce a shift from 489 cm-' to 470 cm-'.…”

Differential Characterization of Neutrophil Cytochrome p30 and Cytochrome b‐558 by Low‐Temperature Absorption and Resonance Raman Spectroscopies

“…2B), showing that the heme iron of cyt p30 is coordinated with the imidazole moiety of two histidyl residues, as in cyt h, and cyt h, (Kitagawa et al, 1982;Desbois et al, 1989;Silvestrini et al, 1993). Cytochrome h-562, in which the heme is coordinated by HislMet residues, exhibits a o,, mode at a significantly higher frequency (1548 cm-'; Bullock and Myers, 1978; Table 2).…”

“…Moreover, it is interesting to note that the HS heme of cyt p30 Selected porphyrin modes of ferric cytochromes b and model complexes. bZ, Desbois et al (1989); Silvestrini et al (1993);b-562, Bullock and Myer (1978); FePP(Im),, imidazole and imidazolate complexes of Fe(I1)-protoporphyrin Desbois and Lutz, 1992); MbF, fluoro-, and Mb(H20) aquo-metmyoglobin, and FePP(MeZSO),, bis(dimethylsu1foxide) complex of Fe(II1)-protoporphyrin Andersson et al, 1985); FePP(CI), chloride complex of Fe(II1)-protoporphyrin Desbois et al (1989); Silvestrini et al (1993);b-562, Bullock and Myer (1978); FePP(Im),, imidazole and imidazolate complexes of Fe(I1)-protoporphyrin Desbois and Lutz, 1992); FePP(2MeIm), 2-methylimidazole, 2-methylimidazolate, and FePP(His), histidine and histidinate complexes of Fe(I1)-protoporphyrin Othman et al, 1993, and unpublished spectra (Ozaki et al, 1986). Since there is no evidence for an electronic transition in the 600-700-nm region of absorption spectra of cyt p30, the HS heme cannot be associated with an Fe-chlorin.…”