Effects of cholesterol and adrenodoxin binding on the heme moiety of cytochrome P-450scc: a resonance Raman study

Tsubaki, Motonari; Hiwatashi, Atsuo; Ichikawa, Yoshiyuki

doi:10.1021/bi00360a014

Cited by 49 publications

(83 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In principle it is possible that the orientation to the heme in all substates is exactly the follow the trend observed for the average values-namely, larger CO-heme normal angles correspond to smaller CO stretch frequencies (23,24). Within the Al band, however, the behavior is opposite.…”

Section: Resultsmentioning

confidence: 70%

“…Fig. 4 shows a correlation between the center frequencies of the A bands and the average orientation of the bound CO in MbCO: Higher CO stretch frequencies correspond to CO orientations closer to the heme normal (21)(22)(23). The Ao substate, where the CO stretch frequency is closest to that of CO bound to protoheme, is closest to being perpendicular to the heme plane, establishing internal consistency.…”

Section: Resultsmentioning

confidence: 80%

See 1 more Smart Citation

Orientation of carbon monoxide and structure-function relationship in carbonmonoxymyoglobin.

Ormos

Braunstein

Frauenfelder

et al. 1988

Proc. Natl. Acad. Sci. U.S.A.

102

View full text Add to dashboard Cite

Fourier transform infrared spectroscopy of the CO stretch bands in carbonmonoxymyoglobin (MbCO) reveals three major bands implying that MbCO exists in three major substates, AO, A1, and A3. After photolysis at low temperatures the CO is in the heme pocket, and the resulting CO stretch bands represent the B substates. Photoselection experiments determine the orientation of CO in the A (bound) and B (photolyzed) substates: Small fractions of MbCO are photolyzed at 10 K with linearly polarized light at 540 nm. The resulting linear dichroism in the A and B IR bands yields the tilt angle between the heme normal and CO. The average angles are as follows: a(AO) = 150 + 30; a(Al) = 28°± 2°, and a(A3) = 330 + 4°. The A bands are inhomogeneously broadened; the angle a shows a wavenumber dependence within the A bands. The wavenumber dependence is interpreted as a distribution of the tilt angle within the individually inhomogeneous A substates, thus providing a structural parameter to characterize the distribution of the conformational substates. The B substates exhibit no induced linear dichroism; in the photolyzed substates the ligand is randomly oriented with respect to the heme plane. The present results together with earlier data on static and kinetic properties of CO binding to Mb establish relations among spectroscopic, structural, energetic, and functional parameters.Nature uses the heme group as the active center in a wide variety of proteins that perform tasks ranging from oxygen storage in myoglobin (Mb) to enzymatic reactions in cytochrome P450 and peroxidases (1). Consequently, the protein structure surrounding the heme group must determine and control function. The details of the connection between structure and function are only partially understood, even in the simple cases of the binding of dioxygen and carbon monoxide (CO) to Mb. We show here that photoselection experiments contribute to the elucidation of the relationship between structure and function by relating spectroscopic, functional, and structural properties.The crucial spectroscopic information is contained in the IR stretch frequency v(C-O) of the bound and photodissociated CO. The stretch frequency shows a strong influence of protein structure: While protoheme-CO has only one stretch band centered at 1964 cm-1, carbonmonoxymyoglobin (MbCO) has three major bands, AO at 1966 cm-1, A1 at 1945 cm-1, and A3 at 1929 cm-1 (2-4). The stretch bands are assigned to three different conformational substates (5), which we call AO, A1, and A3, and which are interpreted as belonging to three slightly different protein conformations (4, 6). Above 220 K the MbCO molecules interconvert among the A substates, whereas below 160 K large-scale protein fluctuations are frozen out, so that each protein remains in one of the A substates. Additional spectroscopic evidence comes from low-temperature flash photolysis experiments (6, 7). Below 160 K, the photolyzed CO remains in the heme pocket. At least two different CO stretch bands, B1 and B2, are observable. Th...

show abstract

Section: Resultsmentioning

confidence: 70%

Section: Resultsmentioning

confidence: 80%

Orientation of carbon monoxide and structure-function relationship in carbonmonoxymyoglobin.

Ormos

Braunstein

Frauenfelder

et al. 1988

Proc. Natl. Acad. Sci. U.S.A.

102

View full text Add to dashboard Cite

show abstract

“…On the other hand, we and others have shown that the nature of the guanidine substrate can significantly modify the oxidation chemistry, along with the resulting reaction intermediates and products (41,42,71,72). These considerations led us to address, in this work, the actual role of the guanidinium proton in the mechanism of NOS by analyzing the interactions between the heme active site and the guanidinium moiety of L (41, 55-57, 59, 69, 70) and cytochromes P450 (44,68,(73)(74)(75)(76). In addition to bond angles, the Fe-CO vibrational modes are very sensitive to the electrostatic and polar properties of the heme distal pocket because of changes in the back donation from the iron d* orbital to the empty * CO orbital (44,45).…”

Section: Discussionmentioning

confidence: 99%

Role of Arginine Guanidinium Moiety in Nitric-oxide Synthase Mechanism of Oxygen Activation

Giroud

Moreau

Mattioli

et al. 2010

Journal of Biological Chemistry

View full text Add to dashboard Cite

“…In this context we note that, based upon different spectroscopic techniques, it was suggested that in mammalian P-420 the thiolate is replaced by a hgand which exhibits much weaker electron-donating capabilities [15,. This may either be a histidine or the protonated thiolate residue.…”

Section: Inactivation Of Lm2 and Lm4mentioning

confidence: 91%

Resonance Raman study on the structure of the active sites of microsomal cytochrome P‐450 isozymes LM2 and LM4

Hildebrandt

Greinert

Stier

et al. 1989

European Journal of Biochemistry

View full text Add to dashboard Cite

The isozymes 2 and 4 of rabbit microsonial cytochrome P-450 (LM2, LM4) have been studied by resonance Raman spectroscopy. Based on high quality spectra, a vibrational assignment of the porphyrin modes in the frequency range between 100 -1700 cm-' is presented for different ferric states of cytochrome P-450 LM2 and LM4. The resonance Raman spectra are interpreted in terms of the spin and ligation state of the heme iron and of heme ~ protein interactions. While in cytochrome P-450 LM2 the six-coordinated low-spin configuration is prcdominantly occupied, in the isozyme LM4 the five-coordinated high-spin form is the most stable state. The different stability of these two spin configurations in LM2 and LM4 can be attributed to the structures of the active sites. In the low-spin form of the isozymes LM4 the protein matrix forces the heme into a more rigid conformation than in LM2. Thcsc steric constraints are removed upon dissociation of the sixth ligand leading to a more flexible structure of the active site in the high-spin form of the isozyme LM4.The vibrational modes of thc vinyl groups were found to be characteristic markers for the specific structures of the heme pockets in both isozymes. They also respond sensitively to type-I substrate binding. Whilc in cytochrome P-450 LM4 the occupation of the substrate-binding pocket induces conformational changes of the vinyl groups, as reflectcd by frequency shifts of the vinyl modes, in the LM2 isozyme the ground-state conformation of these substituents remain unaffected, suggesting that the more flexible heme pocket can accomodate substrates without imposing steric constraints on the porphyrin. The resonance Raman technique makes structural changes visible which are induced by substrate binding in addition and independent of the changes associated with the shift of the spin state equilibrium : the high-spin states in the substrate-bound and substratc-free enzyme are structrually different. The formation of the inactive form, P-420, involves a severe struclural rearrangement in the heme binding pocket leading to drastic changes of the vinyl group conformations. The conformational differcnces of the active sites in cytochromes P-450 LM2 and LM4 observed in this work contribute to the understanding of the structural basis accounting for substrate and product specificity of cytochrome P-450 isozymes.

show abstract

Effects of cholesterol and adrenodoxin binding on the heme moiety of cytochrome P-450scc: a resonance Raman study

Cited by 49 publications

References 37 publications

Orientation of carbon monoxide and structure-function relationship in carbonmonoxymyoglobin.

Orientation of carbon monoxide and structure-function relationship in carbonmonoxymyoglobin.

Role of Arginine Guanidinium Moiety in Nitric-oxide Synthase Mechanism of Oxygen Activation

Resonance Raman study on the structure of the active sites of microsomal cytochrome P‐450 isozymes LM2 and LM4

Contact Info

Product

Resources

About