Proximal ligand motions in H93G myoglobin

Franzen, Stefan; Peterson, Eric S.; Brown, D. B.; Friedman, Joel M.; Thomas, Melissa R.; Boxer, Steven G.

doi:10.1046/j.1432-1033.2002.03193.x

Cited by 16 publications

(26 citation statements)

References 46 publications

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“…On the other hand, if the usual assignment of this mode to the Fe-His vibration is made, its observation in the 10 ns transient Raman spectra provides strong evidence for a heme-histidine bond in the CO-bound forms of P420 13 and, by analogy, iNOS 10 . Such an assignment is also consistent with previous transient Raman studies of the H93G-CO photoproduct 26 .…”

Section: Resultssupporting

confidence: 91%

“…S5). This suggests that, as for H93G-CO 25, 26 , there is a rapid loss of the His ligand upon CO photodissociation (i.e., k Ex >> k γ (k out /k BA H +k out +k Ex ) in Scheme I below). Moreover, there must be a relatively rapid reset rate, k Re , to the initial His bound ligation state (A H ) following CO binding.…”

Section: Discussionmentioning

confidence: 96%

“…The binding of His64 was previously excluded by resonance Raman spectra of the CO bound H64V/H93G double mutant, which is very similar to that of H93G MbCO 25 . Based on transient Raman spectra that detects the 220 cm −1 Fe-His mode, His97 was assigned as the prime candidate to be the trans ligand when CO binds and acidifies the heme iron 26 . When CO is photolyzed, the time resolved step-scan infrared data indicate 26 that the histidine ligand is replaced by water on a time-scale that is faster than ~10 6 s −1 and that the histidine ligand does not rebind until CO bimolecular rebinding takes place 25 .…”

Section: Discussionmentioning

confidence: 99%

“…Earlier work has shown that the affinity of CO bound heme for imidazole is ~10 5 times larger than its affinity for a weak ligand such as water 23 . This concept has been used previously, both in the context of low pH MbCO ligation kinetics 24 and in prior studies of ligand switching in H93G-CO 25, 26 ; it is extended here to account for Raman observations in the P420 system.…”

Section: Introductionmentioning

confidence: 99%

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Investigations of Heme Ligation and Ligand Switching in Cytochromes P450 and P420

et al. 2013

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It is generally accepted that the inactive P420 form of cytochrome P450 (CYP) involves the protonation of the native cysteine thiolate to form a neutral thiol heme ligand. On the other hand, it has also been suggested that recruitment of a histidine to replace the native cysteine thiolate ligand might underlie the P450→P420 transition. Here we discuss resonance Raman investigations of the H93G myoglobin (Mb) mutant in the presence of tetrahydrothiophene (THT) or cyclopentathiol (CPSH), and on pressure-induced cytochrome P420cam (CYP101), that show a histidine becomes the heme ligand upon CO binding. The Raman mode near 220 cm−1, normally associated with the Fe-histidine vibration in heme proteins, is not observed in either reduced P420cam or the reduced H93G Mb samples, indicating that histidine is not the ligand in the reduced state. The absence of a mode near 220 cm−1 is also inconsistent with a generalization of the suggestion that the 221 cm−1 Raman mode, observed in the P420-CO photoproduct of inducible nitric oxide synthase (iNOS), arises from a thiol-bound ferrous heme. This leads us to assign the 218 cm−1 mode observed in the 10 ns P420cam-CO photoproduct Raman spectrum to a Fe-histidine vibration, in analogy to many other histidine bound heme systems. Additionally, the inverse correlation plots of the νFe-His and νCO frequencies for the CO adducts of P420cam and the H93G analogs provide supporting evidence that histidine is the heme ligand in the P420-CO bound state. We conclude that, when CO binds to the ferrous P420 state, a histidine ligand is recruited as the heme ligand. The common existence of a HXC-Fe motif in many CYP systems allows the C→H ligand switch to occur with only minor conformational changes. One suggested conformation of P420-CO involves the addition of another turn in the proximal L helix so that, when the protonated Cys ligand is dissociated from the heme, it can become part of the helix and the heme is ligated by the His residue from the adjoining loop region. In other systems, such as iNOS and CYP3A4 (where the HXC-Fe motif is not found) a somewhat larger conformational change would be necessary to recuit a nearby histidine.

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Section: Resultssupporting

confidence: 91%

Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Investigations of Heme Ligation and Ligand Switching in Cytochromes P450 and P420

et al. 2013

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“…The proximal histidine has been linked with ligand conformational changes in response to dynamic motions of myoglobin on the nanosecond and longer time scales. 31 Additionally, there is another histidine localized distal but not attached to the heme (His 64) that is conserved within the globin subfamily and is in a position suitable for hydrogen-bond formation to the ligand. The distal histidine is thought to have a strong inuence on the protein-ligand binding kinetics.…”

Section: Resultsmentioning

confidence: 99%

Using THz time-scale infrared spectroscopy to examine the role of collective, thermal fluctuations in the formation of myoglobin allosteric communication pathways and ligand specificity

Woods

2014

Soft Matter

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In this investigation we use THz time-scale spectroscopy to conduct an initial set of studies on myoglobin with the aim of providing further insight into the global, collective thermal fluctuations in the protein that have been hypothesized to play a prominent role in the dynamic formation of transient ligand channels as well as in shaping the molecular level basis for ligand discrimination. Using the two ligands O2 and CO, we have determined that the perturbation from the heme-ligand complex has a strong influence on the characteristics of the myoglobin collective dynamics that are excited upon binding. Further, the differences detected in the collective protein motions in Mb-O2 compared with those in Mb-CO appear to be intimately tied with the pathways of long-range allosteric communication in the protein, which ultimately determine the trajectories selected by the respective ligands on the path to and from the heme-binding cavity.

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Systematic Regulation of the Enzymatic Activity of Phenylacetaldoxime Dehydratase by Exogenous Ligands

Kobayashi¹,

Kubo²,

Shiro³

et al. 2006

ChemBioChem

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Phenylacetaldoxime dehydratase from Bacillus sp. OxB-1 (OxdB) contains a heme that acts as the active site for the dehydration reaction of aldoxime. Ferrous heme is the active form, in which the heme is five coordinate with His282 as a proximal ligand. In this work, we evaluated the functional role of the proximal ligand for the catalytic properties of the enzyme by "the cavity mutant technique". The H282G mutant of OxdB lost enzymatic activity, although the heme, which was five coordinate with a water molecule (or OH-) as an axial ligand, existed in the protein matrix. The enzymatic activity was rescued by imidazole or pyridine derivatives that acted as the exogenous proximal ligand. By changing the electron-donation ability of the exogenous ligand with different substituents, the enzymatic activity could be regulated systematically. The stronger the electron-donation ability of the exogenous ligand, the higher was the restored enzymatic activity. Interestingly, H282G OxdB with 2-methyl imidazole showed a higher activity than the wild-type enzyme. Kinetic analyses revealed that the proximal His regulated not only the affinity of substrate binding to the heme but also the elimination of the OH group from the substrate.

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Proximal ligand motions in H93G myoglobin

Cited by 16 publications

References 46 publications

Investigations of Heme Ligation and Ligand Switching in Cytochromes P450 and P420

Investigations of Heme Ligation and Ligand Switching in Cytochromes P450 and P420

Using THz time-scale infrared spectroscopy to examine the role of collective, thermal fluctuations in the formation of myoglobin allosteric communication pathways and ligand specificity

Systematic Regulation of the Enzymatic Activity of Phenylacetaldoxime Dehydratase by Exogenous Ligands

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