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Turner DB, Dinshaw R, Lee KK, Belsley MS, Wilk KE, Curmi PMG, Scholes GD. Quantitative investigations of quantum coherence for a light-harvesting protein at conditions simulating photosynthesis. Phys Chem Chem Phys 2012; 14:4857-74. [PMID: 22374579 DOI: 10.1039/c2cp23670b] [Citation(s) in RCA: 150] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Recent measurements using two-dimensional electronic spectroscopy (2D ES) have shown that the initial dynamic response of photosynthetic proteins can involve quantum coherence. We show how electronic coherence can be differentiated from vibrational coherence in 2D ES. On that basis we conclude that both electronic and vibrational coherences are observed in the phycobiliprotein light-harvesting complex PC645 from Chroomonas sp. CCMP270 at ambient temperature. These light-harvesting antenna proteins of the cryptophyte algae are suspended in the lumen, where the pH drops significantly under sustained illumination by sunlight. Here we measured 2D ES of PC645 at increasing levels of acidity to determine if the change in pH affects the quantum coherence; quantitative analysis reveals that the dynamics are insensitive to the pH change.
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Affiliation(s)
- Daniel B Turner
- Department of Chemistry, Institute for Optical Sciences, and Centre for Quantum Information and Quantum Control, 80 St. George Street, Toronto, Ontario, M5S 3H6, Canada
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2
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Thoren KL, Connell KB, Robinson TE, Shellhamer DD, Tammaro MS, Gindt YM. The free energy of dissociation of oligomeric structure in phycocyanin is not linear with denaturant. Biochemistry 2006. [PMID: 17002304 DOI: 10.1021/bi061140] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Using SEC HPLC and fluorescence anisotropy, absorption spectra were assigned to the specific oligomeric structures found with phycocyanin. The absorption spectra were used to quantify the population of each oligomeric form of the protein as a function of both urea concentration and temperature. Phycocyanin hexamers dissociate to trimers with equilibrium constants of 10(-6) to 10(-5). Phycocyanin trimers dissociate to monomers with equilibrium constants of 10(-15) to 10(-12). Both dissociation constants increase linearly with increasing urea concentration, and deltaG(o) values calculated from the equilibrium constants fit best with an exponential function. Our findings appear in contrast with the commonly used linear extrapolation model, deltaG(urea)(o) = deltaG(water)(o) + A[denaturant], in which a linear relationship exists between the free energy of protein unfolding or loss of quaternary structure and the denaturant concentration. Our data examines a smaller range of denaturant concentration than generally used, which might partially explain the inconsistency.
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Affiliation(s)
- Katie L Thoren
- Department of Chemistry, Lafayette College, Easton, Pennsylvania 18042, USA
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4
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Thoren KL, Connell KB, Robinson TE, Shellhamer DD, Tammaro MS, Gindt YM. The free energy of dissociation of oligomeric structure in phycocyanin is not linear with denaturant. Biochemistry 2006; 45:12050-9. [PMID: 17002304 PMCID: PMC2519023 DOI: 10.1021/bi061140+] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Using SEC HPLC and fluorescence anisotropy, absorption spectra were assigned to the specific oligomeric structures found with phycocyanin. The absorption spectra were used to quantify the population of each oligomeric form of the protein as a function of both urea concentration and temperature. Phycocyanin hexamers dissociate to trimers with equilibrium constants of 10(-6) to 10(-5). Phycocyanin trimers dissociate to monomers with equilibrium constants of 10(-15) to 10(-12). Both dissociation constants increase linearly with increasing urea concentration, and deltaG(o) values calculated from the equilibrium constants fit best with an exponential function. Our findings appear in contrast with the commonly used linear extrapolation model, deltaG(urea)(o) = deltaG(water)(o) + A[denaturant], in which a linear relationship exists between the free energy of protein unfolding or loss of quaternary structure and the denaturant concentration. Our data examines a smaller range of denaturant concentration than generally used, which might partially explain the inconsistency.
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Affiliation(s)
- Katie L Thoren
- Department of Chemistry, Lafayette College, Easton, Pennsylvania 18042, USA
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5
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Zubova NN, Korolenko VA, Astafyev AA, Petrukhin AN, Vinokurov LM, Sarkisov OM, Savitsky AP. Brightness of Yellow Fluorescent Protein from Coral (zFP538) Depends on Aggregation. Biochemistry 2005; 44:3982-93. [PMID: 15751974 DOI: 10.1021/bi048274c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The yellow fluorescent protein from coral (zFP538) forms aggregates in water solutions. According to dynamic light scattering and gel filtration data, the aggregation number is approximately 1000-10000 at pH 8-9 and protein concentration 1 mg/mL. Gel filtration demonstrated that dissociation of the aggregates takes place upon dilution, and the molecular weight of the aggregates decreases with pH. Atomic force microscopy (AFM) and near-field scanning optical microscopy (NSOM) were used to obtain images of zFP538 in the solid state. It was shown that protein films are comprised of fluorescent ellipsoidal granules with a 50-300 nm major axis and a 30-130 nm minor axis. The dependence of zFP538 fluorescence on protein concentration between 1.2 x 10(-)(9) and 5.5 x 10(-)(7) M can be divided in two linear regions with different slopes indicating the existence of at least two different forms of zFP538. The fluorescence of zFP538 decreases with time upon acidification, and the decrease depends on pH and protein concentration. Between pH 3.5 and pH 5.5, relative residual fluorescence is higher for concentrated zFP538 solutions (about 10(-)(6) M) as compared with diluted ones (10(-)(7) M and below). Aggregation makes zFP538 more stable against fluorescence quenching upon acidification: the decrease in zFP538 fluorescence at protein concentration 1 mg/mL is completely reversible, unlike that observed for less concentrated solutions. This phenomenon may be due to the decrease in the freedom of chromophore mobility in zFP538 aggregates.
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Affiliation(s)
- Nadezhda N Zubova
- Faculty of Chemistry, Department of Chemical Enzymology, M. V. Lomonosov Moscow State University, Vorob'ovy Gory, 119992 Moscow, Russia
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6
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Doust AB, Marai CNJ, Harrop SJ, Wilk KE, Curmi PMG, Scholes GD. Developing a structure-function model for the cryptophyte phycoerythrin 545 using ultrahigh resolution crystallography and ultrafast laser spectroscopy. J Mol Biol 2004; 344:135-53. [PMID: 15504407 DOI: 10.1016/j.jmb.2004.09.044] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2004] [Revised: 09/17/2004] [Accepted: 09/20/2004] [Indexed: 10/26/2022]
Abstract
Cryptophyte algae differ from cyanobacteria and red algae in the architecture of their photosynthetic light harvesting systems, even though all three are evolutionarily related. Central to cryptophyte light harvesting is the soluble antenna protein phycoerythrin 545 (PE545). The ultrahigh resolution crystal structure of PE545, isolated from a unicellular cryptophyte Rhodomonas CS24, is reported at both 1.1A and 0.97A resolution, revealing details of the conformation and environments of the chromophores. Absorption, emission and polarized steady state spectroscopy (298K, 77K), as well as ultrafast (20fs time resolution) measurements of population dynamics are reported. Coupled with complementary quantum chemical calculations of electronic transitions of the bilins, these enable assignment of spectral absorption characteristics to each chromophore in the structure. Spectral differences between the tetrapyrrole pigments due to chemical differences between bilins, as well as their binding and interaction with the local protein environment are described. Based on these assignments, and considering customized optical properties such as strong coupling, a model for light harvesting by PE545 is developed which explains the fast, directional harvesting of excitation energy. The excitation energy is funnelled from four peripheral pigments (beta158,beta82) into a central chromophore dimer (beta50/beta61) in approximately 1ps. Those chromophores, in turn, transfer the excitation energy to the red absorbing molecules located at the periphery of the complex in approximately 4ps. A final resonance energy transfer step sensitizes just one of the alpha19 bilins on a time scale of 22ps. Furthermore, it is concluded that binding of PE545 to the thylakoid membrane is not essential for efficient energy transfer to the integral membrane chlorophyll a-containing complexes associated with PS-II.
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Affiliation(s)
- Alexander B Doust
- Lash-Miller Chemical Laboratories, University of Toronto, 80 St George Street, Toronto, Ontario, Canada M5S 3H6
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MacColl R, Eisele LE, Marrone J. Fluorescence polarization studies on four biliproteins and a bilin model for phycoerythrin 545. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1412:230-9. [PMID: 10482785 DOI: 10.1016/s0005-2728(99)00063-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Fluorescence (excitation) polarization spectroscopy in the wavelength region of the bilin chromophores was applied to phycoerythrocyanin (CV-phycocyanin), phycocyanins 645 and 612, and phycoerythrin 545. The cryptomonad biliproteins - phycoerythrin 545 and phycocyanins 612 and 645 - were studied as both protein dimers having an alpha(2)beta(2) polypeptide structure and as alphabeta monomers. The cyanobacterial phycoerythrocyanin (CV-phycocyanin) was a trimeric oligomer. The changes in polarization across the spectrum were attributed to transfers of energy between bilins. Cryptomonad biliproteins are isolated as dimers. The similarities between their steady-state fluorescence polarization spectra and those of the corresponding monomers suggested that the monomers' conformations were analogous to the dimers. This supports the use of monomers in the study of dimer bilin organization. The unusual polarization spectrum of phycoerythrin 545 was explained using a model for the topography of its bilins. Obtaining the emission spectra of phycoerythrin 545 at several temperatures and a deconvolution of the dimer circular dichroism spectrum also successfully tested the bilin model. Circular dichroism spectroscopy was used to determine which polarization changes are formed by Förster resonance energy transfers and which may be produced by internal conversions between high- and low-energy states of pairs of exciton-coupled bilins. Attempts were made to assign energy transfer events to the corresponding changes in fluorescence polarization for each of the four biliproteins.
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Affiliation(s)
- R MacColl
- Wadsworth Center, New York State Department of Health, P.O. Box 509, Albany, NY, USA.
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MacColl R, Eisele LE, Dhar M, Ecuyer JP, Hopkins S, Marrone J, Barnard R, Malak H, Lewitus AJ. Bilin organization in cryptomonad biliproteins. Biochemistry 1999; 38:4097-105. [PMID: 10194324 DOI: 10.1021/bi982059c] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The bilin organization of three cryptomonad biliproteins (phycocyanins 612 and 645 and phycoerythrin 545) was examined in detail. Two others (phycocyanin 630 and phycoerythrin 566) were studied less extensively. Phycocyanin 645 and phycoerythrin 545 were suggested to have one bilin in each monomeric (alphabeta) unit of the dimer (alpha2beta2) isolated from the others, and the remaining six bilins may be in pairs. One pair was found across the monomer-monomer interface of the protein dimer, and two identical pairs were proposed to be within the monomer protein units. For phycocyanin 612, a major surprise was that a pair of bilins was apparently not found across the monomer-monomer interface, but the remaining bilins were distributed as in the other two cryptomonad proteins. The effect of temperature on the CD spectra of phycocyainin 612 demonstrated that two of the bands (one positive and one negative) behaved identically, which is required if they are coupled. The two lowest-energy CD bands of phycocyanin 612 originated from paired bilins, and the two higher-energy bands were from more isolated bilins. The paired bilins within the protein monomers contained the lowest-energy transition for these biliproteins. Using the bilins as naturally occurring reporter groups, phycocyanin 612 was shown to undergo a reversible change in tertiary structure at 40 degrees C. Protein monomers were shown to be functioning biliproteins. A hypothesis is that the coupled pair of bilins within the monomeric units offers important advantages for efficient energy migration, and other bilins transfer energy to this pair, extending the wavelength range or efficiency of light absorption.
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Affiliation(s)
- R MacColl
- Wadsworth Center, New York State Department of Health, Albany 12201-0509, USA.
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Abstract
Cyanobacterial phycobilisomes harvest light and cause energy migration usually toward photosystem II reaction centers. Energy transfer from phycobilisomes directly to photosystem I may occur under certain light conditions. The phycobilisomes are highly organized complexes of various biliproteins and linker polypeptides. Phycobilisomes are composed of rods and a core. The biliproteins have their bilins (chromophores) arranged to produce rapid and directional energy migration through the phycobilisomes and to chlorophyll a in the thylakoid membrane. The modulation of the energy levels of the four chemically different bilins by a variety of influences produces more efficient light harvesting and energy migration. Acclimation of cyanobacterial phycobilisomes to growth light by complementary chromatic adaptation is a complex process that changes the ratio of phycocyanin to phycoerythrin in rods of certain phycobilisomes to improve light harvesting in changing habitats. The linkers govern the assembly of the biliproteins into phycobilisomes, and, even if colorless, in certain cases they have been shown to improve the energy migration process. The Lcm polypeptide has several functions, including the linker function of determining the organization of the phycobilisome cores. Details of how linkers perform their tasks are still topics of interest. The transfer of excitation energy from bilin to bilin is considered, particularly for monomers and trimers of C-phycocyanin, phycoerythrocyanin, and allophycocyanin. Phycobilisomes are one of the ways cyanobacteria thrive in varying and sometimes extreme habitats. Various biliprotein properties perhaps not related to photosynthesis are considered: the photoreversibility of phycoviolobilin, biophysical studies, and biliproteins in evolution. Copyright 1998 Academic Press.
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Affiliation(s)
- R MacColl
- Wadsworth Center, New York State Department of Health, Albany, New York, 12201-0509, USA
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Bieniarz C, Cornwell MJ, Young DF. Alkaline phosphatase activatable polymeric cross-linkers and their use in the stabilization of proteins. Bioconjug Chem 1998; 9:390-8. [PMID: 9576814 DOI: 10.1021/bc9800264] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
We report the synthesis of polymeric cross-linking agents, poly(glutamic acid) poly(phosphorothioates), and their use in the cross-linking and stabilization of proteins upon treatment with alkaline phosphatase. We have shown that poly(phosphorothioates) are excellent substrates of alkaline phosphatase, yielding thiolated polymers which react covalently with electrophilic groups introduced into the proteins. Three proteins of different structure and function were cross-linked using this method: calf intestinal alkaline phosphatase, glucose oxidase (Aspergillus niger), and (R)-phycoerythrin. The cross-linking of alkaline phosphatase is self-catalyzed since this enzyme catalyzes the hydrolysis of phosphates, unmasking thiolates which react with the maleimide prederivatized alkaline phosphatase. Incubation of buffered solutions of native alkaline phosphatase at 45 degreesC for 7-14 days resulted in a 35% higher loss of enzymatic activity compared to that of cross-linked enzyme. The effect of cross-linking glucose oxidase is even more notable, ranging from 800% stabilization at 37 degrees C and pH 9.0 to 3000% at 37 degrees C and pH 7.4. (R)-Phycoerythrin cross-linked with 1-3 equiv of poly(phosphorothioates) and incubated at 45 degrees C for 45 days was 20% more fluorescent than the native (R)-phycoerythrin subjected to the same conditions. The stabilizing effect of cross-linking was confirmed by comparing the rate of loss of quaternary structure of the cross-linked (R)-phycoerythrin with that of the native protein.
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Affiliation(s)
- C Bieniarz
- Advanced Drug Delivery, Abbott Laboratories, Abbott Park, Illinois 60064-3500, USA.
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MacColl R, Malak H, Gryczynski I, Eisele LE, Mizejewski GJ, Franklin E, Sheikh H, Montellese D, Hopkins S, MacColl LC. Phycoerythrin 545: monomers, energy migration, bilin topography, and monomer/dimer equilibrium. Biochemistry 1998; 37:417-23. [PMID: 9425063 DOI: 10.1021/bi971453s] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Phycoerythrin 545 was isolated having an alpha2beta2 (dimer) protein structure at pH 6.0 and 2 g/L protein concentration with eight bilin chromophores. Monomers (alphabeta) were produced by lowering the protein concentration to 0.15 g/L and the pH to 4.5. Dimer dissociation was monitored by dynamic light scattering and gel-filtration column chromatography. Monomers were stable and had bilin optical spectra different from the alpha2beta2 dimers, although they have very similar protein secondary structures. The optical spectra of phycoerythrin 545 showed four types of behavior with temperature: 10-20 degrees C, dimers; 40-50 degrees C, dimers/monomers; 60 degrees C, nearly fully disordered; 70 degrees C, disordered alpha and beta polypeptides. At 40 degrees C, the protein dissociated partially to monomer, which could be totally reversed to dimers at 20-25 degrees C. The visible circular dichroism difference spectrum for the protein dimers minus monomers exhibited positive and negative bands--such spectra may indicate exciton splitting between closely-spaced bilins. Circular dichroism also revealed a spectrum suggesting exciton coupling for the second excited state of the bilins. Ultrafast fluorescence using a two-photon method showed the fastest time for protein dimers to be 2. 4 ps and monomers had a 39-ps lifetime. Phycocyanin 645 was found to have a 550-fs lifetime.
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Affiliation(s)
- R MacColl
- Wadsworth Center, New York State Department of Health, Albany, New York 12201-0509, USA.
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Edwards MR, Hauer C, Stack RF, Eisele LE, MacColl R. Thermophilic C-phycocyanin: effect of temperature, monomer stability, and structure. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1997. [DOI: 10.1016/s0005-2728(97)00056-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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MacColl R, Kapoor S, Montellese DR, Kukadia S, Eisele LE. Bilin chromophores as reporters of unique protein conformations of phycocyanin 645. Biochemistry 1996; 35:15436-9. [PMID: 8952496 DOI: 10.1021/bi961334x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
At 45 degrees C, phycocyanin 645 maximally undergoes a reversible and stable conformational change. The change is observed in the visible (chromophore) region of the absorption and circular dichroism (CD) spectra. In the absorption spectrum, the absorbance is lower at 45 degrees C but remains much closer to the normal spectrum than to a strongly denatured spectrum. In the CD, a similar situation exists except that a negative band on the blue edge of the spectrum is much more strongly affected at 45 degrees C than the other bands. On returning to 20 degrees C, all these changes are restored to the original states. The protein is an alpha 2 beta 2 dimer at both 20 and 45 degrees C, and CD in the far-UV shows the identical protein secondary structures at both 20 and 45 degrees C. Fluorescence studies show that energy transfer occurs at both temperatures. At 50 degrees C the results are saliently different as the secondary structure changes and the spectral changes are mostly irreversible. At 50 degrees C, some monomers (alpha beta) are produced, and these monomers are very unstable at that temperature, resulting in the formation of some fully denatured polypeptides. Stable monomers can be produced at 20 degrees C and have visible absorption and CD spectra identical to the dimer at 45 degrees C. Therefore, the chromophores are reporting a tertiary conformational change at 45 degrees C, in which the two halves of the dimer each assume a monomer-like conformation prior to dissociating. These results are compared with a hypothesis for the chromophore topography, and the CD change at the blue edge of the spectra may result from the separation at 45 degrees C of a chromophore pair.
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Affiliation(s)
- R MacColl
- Wadsworth Center, New York State Department of Health, Albany 12201-0509, USA.
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Edwards MR, MacColl R, Eisele LE. Some physical properties of an unusual C-phycocyanin isolated from a photosynthetic thermophile. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1996. [DOI: 10.1016/0005-2728(96)00032-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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MacColl R, Eisele LE, Williams EC, Bowser SS. The discovery of a novel R-phycoerythrin from an antarctic red alga. J Biol Chem 1996; 271:17157-60. [PMID: 8663533 DOI: 10.1074/jbc.271.29.17157] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
A novel biliprotein, named R-phycoerythrin IV, has been discovered. It absorbs blue light better than any other known red algal biliprotein. The protein was found in Phyllophora antarctica, a benthic macroalga, which grows beneath the coastal waters of McMurdo Sound, Antarctica. Fluorescence emission and fluorescence excitation polarization spectroscopy demonstrated that R-phycoerythrin IV behaved as a typical R-phycoerythrin in the functioning of energy migration and has an emission maximum at 577 nm. The circular dichroism (CD) spectrum of the chromophores was compared with visible absorption spectrum, and both were deconvoluted. This process showed the energy states of various individual chromophores. The molecular weight of the protein suggested a alpha6beta6gamma polypeptide structure, and far UV CD studies revealed polypeptides with highly alpha-helical secondary structures. Dynamic light scattering indicated that the protein had a 5.54 nm radius, and its shape was nonspherical. R-phycoerythrin was also purified from a second benthic Antarctic red alga, Iridaea cordata. Its spectroscopic properties were similar to those of some R-phycoerythrins from nonpolar regions. The unique spectroscopic properties of R-phycocerythrin IV may help enable the alga to occupy its niche deeper in the water column than the red alga that has the typical R-phycoerythrin.
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Affiliation(s)
- R MacColl
- Wadsworth Center, New York State Department of Health, Albany, New York 12201-0509, USA
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