Nanosecond Step-Scan FTIR Spectroscopy of Hemoglobin:  Ligand Recombination and Protein Conformational Changes

Hu, Xuehua; Frei, Heinz; Spiro, Thomas G.

doi:10.1021/bi961522n

Cited by 45 publications

(39 citation statements)

References 31 publications

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“…52,53 The rise at early times reflects geminate recombination and is modeled with t gem ¼ 70 ns, the time constant obtained (more accurately than the present data allow) from FTIR monitoring of the hemebound CO stretching band. 22,26 The rise at late times reflects second-order binding of CO from solution, and is modeled with t 4 ¼ 200 ms and t 5 ¼ 1:5 ms exponentials, in agreement with the TA values. The long plateau at intermediate times provides an accurate measurement of the geminate yield.…”

Section: Transient Absorptionsupporting

confidence: 57%

“…We have used resonance Raman (RR), particularly with excitation at ultraviolet wavelengths (UVRR), 18 -20,23 -25 and infrared 22,26 spectroscopies to probe the protein structure following photodeligation of the CO ligand in HbCO. Kinetic analysis of spectral intensities produced time-constants that were consistent with previous studies of visible absorption transients, and permitted extraction of the vibrational spectra of protein intermediates lying on the T -R pathway.…”

Section: Introductionmentioning

confidence: 99%

“…The continuous line is computed with t gem ¼ 0:070 ms (from IR monitoring of geminate recombination22,26 ), and t 4 ¼ 200 ms, t 5 ¼ 1:5 ms, representing rebinding from solution.…”

mentioning

confidence: 99%

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Time-resolved Absorption and UV Resonance Raman Spectra Reveal Stepwise Formation of T Quaternary Contacts in the Allosteric Pathway of Hemoglobin

Balakrishnan

Case

Pevsner

et al. 2004

Journal of Molecular Biology

158

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Section: Transient Absorptionsupporting

confidence: 57%

Section: Introductionmentioning

confidence: 99%

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Time-resolved Absorption and UV Resonance Raman Spectra Reveal Stepwise Formation of T Quaternary Contacts in the Allosteric Pathway of Hemoglobin

Balakrishnan

Case

Pevsner

et al. 2004

Journal of Molecular Biology

158

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“…An extensive number of kinetic and equilibrium studies on the association/dissociation of O 2 and CO to/from myoglobin (including heme distal mutants) have been performed (36,37,38). From the data, it is clear that first, there is no defined relationship between the Fe-C-O geometry and CO affinity.…”

Section: Discussionmentioning

confidence: 99%

Binding of Oxygen and Carbon Monoxide to a Heme-regulated Phosphodiesterase from Escherichia coli

Taguchi

Matsui

Igarashi

et al. 2004

Journal of Biological Chemistry

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The heme-regulated phosphodiesterase, Ec DOS, is a redox sensor that uses the heme in its PAS domain to regulate catalysis. The rate of O 2 association (k on ) with full-length Ec DOS is extremely slow at 0. 0019 The phosphodiesterase (PDE) 1 from Escherichia coli, Ec DOS, is composed of an N-terminal heme-bound PAS domain and a C-terminal PDE catalytic domain (1). The basic physicochemical characteristics and function of this enzyme have been partially elucidated by our group and that of Kitagawa et al. (1,2). PDE activity is dependent on the redox state of Ec DOS in that the enzyme is active only when the heme is in the Fe(II) state. Changes in the redox state of the heme bound to the N-terminal PAS domain may induce a subtle conformational change, which intramolecularly transmits signals to the C-terminal PDE domain to initiate and/or regulate catalysis. Ec DOS therefore constitutes a novel class of heme enzymes designated "heme-based sensors" (3-5). These include proteins such as FixL (6, 7), CooA (8, 9), sGC (10, 11), and Hem-AT (12, 13). In these enzymes, association or dissociation of the exogenous axial ligand (O 2 , CO, or NO) from the heme iron leads to protein conformational changes, which in turn transmit signals to other domains to regulate catalysis or binding to DNA. The Ec DOS signal transducing mechanism appears to be unique, since changes in the redox state of the PAS domain, rather than iron coordination chemistry, are responsible for signal transduction (1). However, in other words, signal transduction triggered by ligand binding (CO and NO) is common to Ec DOS and FixL, based on the finding that CO or NO binding abolishes catalysis by Ec DOS (1).The physicochemical properties of the isolated heme-bound PAS domain of Ec DOS were initially characterized by GillesGonzales and colleagues (14). The kinetics of exogenous axial ligand binding to the heme protein and associated equilibrium constants provide useful information on the structure and characteristics of the heme distal site and ligand access channel (16 -19). It is important to study O 2 and CO binding, particularly to full-length Ec DOS, to clarify whether the enzyme is a direct O 2 sensor. These analyses would also be useful in elucidating the structure of the heme distal site and ligand access channel and their relation to the signal transduction mechanism. Based on the amino acid sequence alignment and crystal structure of a similar PAS enzyme, FixL (7,20,21), Met-95 is suggested as a heme axial ligand trans to His-77.In the present study, we report rate and equilibrium constants for O 2 and CO binding to the full-length enzyme in the Fe(II) state, isolated heme-bound PAS domain, and Met-95 * The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.‡ To whom correspondence should be addressed: Institute of Multidisciplinary Research for Advanced Materials, Tohok...

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“…For radical pair states with lifetimes in the~200 ns to~500 μs range, static excited populations are usually very small, and time resolved (TR) methods are preferred for the collection of FTIR DS associated with the transient species [1]. By far the most widely used approach is time-resolved step-scan (TRSS) FTIR DS [1,[28][29][30][31][32]. For PSI photosynthetic protein complexes, bands in the difference spectra have an intensity that is~1 × 10 −3 (in absorbance or optical density (OD) units) or less [33,34].…”

Section: Introductionmentioning

confidence: 99%

Vibrational spectroscopy of photosystem I

Hastings

2015

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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Fourier transform infrared difference spectroscopy (FTIR DS) has been widely used to study the structural details of electron transfer cofactors (and their binding sites) in many types of photosynthetic protein complexes. This review focuses in particular on work that has been done to investigate the A₁cofactor in photosystem I photosynthetic reaction centers. A review of this subject area last appeared in 2006 [1], so only work undertaken since then will be covered here. Following light excitation of intact photosystem I particles the P700⁺A⁻(1) secondary radical pair state is formed within 100ps. This state decays within 300ns at room temperature, or 300μs at 77K. Given the short-lived nature of this state, it is not easily studied using "static" photo-accumulation FTIR difference techniques at either temperature. Time-resolved techniques are required. This article focuses on the use of time-resolved step-scan FTIR DS for the study of the P700⁺A⁻(1) state in intact photosystem I. Up until now, only our group has undertaken studies in this area. So, in this article, recent work undertaken in our lab is described, where we have used low-temperature (77K), microsecond time-resolved step-scan FTIR DS to study the P700⁺A⁻(1) state in photosystem I. In photosystem I a phylloquinone molecule occupies the A₁binding site. However, different quinones can be incorporated into the A1 binding site, and here work is described for photosystem I particles with plastoquinone-9, 2-phytyl naphthoquinone and 2-methyl naphthoquinone incorporated into the A₁binding site. Studies in which ¹⁸O isotope labeled phylloquinone has been incorporated into the A1 binding site are also discussed. To fully characterize PSI particles with different quinones incorporated into the A1 binding site nanosecond to millisecond visible absorption spectroscopy has been shown to be of considerable value, especially so when undertaken using identical samples under identical conditions to that used in time-resolved step-scan FTIR measurements. In this article the latest work that has been undertaken using both visible and infrared time resolved spectroscopies on the same sample will be described. Finally, vibrational spectroscopic data that has been obtained for phylloquinone in the A1 binding site in photosystem I is compared to corresponding data for ubiquinone in the QA binding site in purple bacterial reaction centers. This article is part of a Special Issue entitled: Vibrational spectroscopies and bioenergetic systems.

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Nanosecond Step-Scan FTIR Spectroscopy of Hemoglobin: Ligand Recombination and Protein Conformational Changes

Cited by 45 publications

References 31 publications

Time-resolved Absorption and UV Resonance Raman Spectra Reveal Stepwise Formation of T Quaternary Contacts in the Allosteric Pathway of Hemoglobin

Time-resolved Absorption and UV Resonance Raman Spectra Reveal Stepwise Formation of T Quaternary Contacts in the Allosteric Pathway of Hemoglobin

Binding of Oxygen and Carbon Monoxide to a Heme-regulated Phosphodiesterase from Escherichia coli

Vibrational spectroscopy of photosystem I

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