1 / 26

«PROBLEM OF ORIGIN OF LIFE»

«PROBLEM OF ORIGIN OF LIFE» International Conference in Honor of 1 2 0 th Birth Anniversary of acad. A.I. Oparin Karapetyan N.V. A.N. Bach Institute of Biochemistry RAS, Moscow How cyanobactria managed to survive under intense solar radiation billions years ago:

Télécharger la présentation

«PROBLEM OF ORIGIN OF LIFE»

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. «PROBLEM OF ORIGIN OF LIFE» International Conference in Honor of 120th Birth Anniversary of acad.A.I. Oparin Karapetyan N.V. A.N. Bach Institute of Biochemistry RAS, Moscow How cyanobactria managed to survive under intense solar radiation billions years ago: Photoprotection mechanisms September 26, 2014

  2. Acad. A.I. Oparin was elected as the firstPresident of ISSOL(photo was taken in Pont-á-Mousson, France 1970) . «You are our Pope, we are your monks!» «Вы наш пастырь, мы Ваши иноки!»

  3. Acad. A.I. Oparin was the Director of A.N. Bach Institute of Biochemistry for 1946-1980 Many laboratories of our Institute have been involved in study of OriginandEvolution of Life. My contribution: “Photoprotecton mechanisms against photodestruction by excess absorbed energy in cyanobacteria.” We have found two mechanisms of photoprotection in cyanobacteria: 1.Carotenoid-less non-photochemical quenching by Photosystem I 2.Carotenoid-induced non-photochemical quenching of Phycobilisomes .

  4. Cyanobacteria, the first photosynthetic organisms, have originated about 2.5-3 Gyrsago in conditions of intense UV and VIS light at the absence of ozone layer. Irradiance conditions on the Earth surface NOW on the width of equator: UV-C (190-280 nm) - does not penetrate the ozone layer UV-B (280-320 nm) - 7-8 W m-2 UV-A (320-400 nm) - 45-50 W m-2 (generates singlet oxygen) VIS light (400-700 nm)- 1100 W m-2 To be protected against intense solar light and UV, cyanobacteria were habituated in deep ocean waters or in hydrothermal sources.

  5. Oxygenic photosynthesis Photosynthesis is optimal under the balance of the activity and stability of the photosynthetic apparatus. Over-excitation of antenna Chls generates reactive oxygen species that destroy the photosynthetic apparatus. Dissipation (or quenching) of excessabsorbed energy protects against photodestruction.

  6. Carotenoid-less non-photochemical quenching by Photosystem I PSI complex exists in cyanobacteria as atrimer, in plants asa monomer. 3.4Å structure of PSI monomer of P. sativum Amunts et al., Nature (2007) 2.5Åstructure of PSI trimer of Th. elongatus Jordan et al., Nature (2001)

  7. Organization of Chlorophyll (Chl) antenna in cyanobacteria Chls in cyanobacteria are located only in core antenna of PSI and PSII since cyanobacteria are deficient in Chl-containing Lhca. Cyanobacteria are highly enriched with PSI: PSI/PSII ratio is 3-5. Thus main part of Chls (~90%) in cyanobacteria is located in PSI. About 90% of antenna Chls in PSI of cyanobacteria belong to bulk while 10% of antenna Chls belong to long-wavelength Chls (LWC). The origin of LWC and the role in PSI was not clear. We have studied the role of the red-most LWC in energy balance and in energy dissipation in the cyanobacterium Arthrospira platensis Some information about LWC of PSI in cyanobacteria.

  8. LWC in PSI coreantenna of cyanobacteria and plants (Gobets…Karapetyan et al., Biophys. J. 2001) 6 K Gaussian deconvolution of 5 K absorption spectrum of PSI trimers of A. platensis: LWC740 (F760)=3; LWC708 (F730)= 7 (Schlodder,….Karapetyan et al., BBA 2005) 730nm 290 K trimer 740 monomer 708

  9. Spectral characteristics of LWC in PSI trimers and monomers of A. platensis andTh. elongatus; amount of Chl molecules - in parenthesis (Karapetyan et al., FEBS Lett. 1999)

  10. Fluorescence DAS (decay associated spectra) LWC delaythe energy equilibration in core antenna and trapping by P700;it is dependent on spectral properties of LWC: 35 ps in PSI trimers of Th. elongatus - C 37 ps in PSI monomers of A. platensis - D 50 ps in PSI trimers of A. platensis - E. (Gobets,.. Karapetyan et al., Biophys. J. 2001) trimer monomer trimer

  11. P700+efficientlyquenches F760 of PSI trimers of A. platensisand F735of PSI trimers of Th. elongatus(Schlodder… Karapetyan, BBA 2011) PSI trimers PSI monomers P700AoA1-FxFA-FB- A. platensis 760 P700+AoA1FXFAFB Th. elongatus

  12. Energy transfer in PSI antenna depends on redox state of the cofactors of the PSI Rection Center (RC): open RC – charge separation Chl →P700A0A1FX→ P700+Ao- A1FX closed RC – dissipation of absorbed energy Chl →P700+A0A1FX or Chl →3P700A0A1-FX P700is involved in charge separation P700+or3P700 are involved in energy dissipation

  13. Origin of LWC: interaction of Chl molecules on the surface of various PSI monomers is forming the red-most LWC (F760) in PSI trimers ofA. platensis(Karapetyan et al., Photosynth. Res. 1999) Time-course of F760 quenching and P700+ formation in PSI trimers of A. platensis at 77K Non-linear dependence of F760 on P700+ amount in PSI trimers of A. platensisindicates on energy exchange between PSI monomers within trimer PSI trimer of Th. elongatus(Jordan et al., 2001)

  14. Localization of LWC in PSI antenna of Th. elongatus: trimer 719 (F741) - 4Chls; 708 (F732) - 4Chls monomer 719 (F730) - 2Chls;708 (F728) - 4Chls Chl719 (F741) might beB7/A32/A31 Chl719 is notB31/B32/B33 – 3 Chls, big distance to P700 (50Å) Candidates for Chl708 (F732) are B38/B37, А38/A39, B18/B19 or A16/A17/A25 (strong coupling between Chls, dig distance to P700). Chl715 (F734) = B24/B25 orA26/A27 F741 F734 F734 F732 Schlodder…Karapetyan, BBA (2012)

  15. Localization of LWC in PSI complexes of A. platensis PSI trimer: 740 (F760) - 3 Chl; 708 (F727) - 7 Chl PSI monomer: 708 (F726) – 7 Chl (three different aggregates). Chl740 (F760)might be A31/A32/B7 on lumenal sideclose to trimerization point, time of energy transfer to P700+ is 110 ps, dipol is oriented parallel to membrane Chl708(F727)=B38/B37, A38/A39B18/B19or A25/A16/A17 Distance between Chl740 and Chl708: Chl740 Chl708 A32/A31/B7to B38/B37= 22Å A32/A31/B7 to A25/A16/A17=48Å A32/A31/B7to А38/A39 = 57Å A32/A31/B7to B18/B19 = 52Å F760 F727 orF727 Schlodder…Karapetyan, BBA (2012)

  16. Different orientation of Chls in various LWC730 of PSI antenna in A. platensis SMS data Fluorescence spectra of a single PSI trimer of as a function of the orientation of polarizer in front of the spectrograph Chls in F730 polarized differently since 2-3 different emitters form this LWC. Chls in F760 are polarized equally. (Brecht,….KarapetyanBBA 2012)

  17. Scheme of energy migration in antenna of PSI trimers of A. platensis No interaction of some LWC708 and LWC740at cryogenic temperatures: - big distance between F760 (А31-A32-B7) and LWC726 (different complexes) - different orientation of the transient dipole moments in LWC708 (Karapetyan et al., Biochemistry-Moscow 2014) Bulk Chl P700 LWC708 F726 LWC708 ~F726 LWC740 F760 А31-A32-B7 P700+ heat

  18. 1. Conclusions: PSI-induced energy dissipation in cyanobacteria 1. LWCdelay the energy equilibration and trapping in PSI core antenna. LWC function as terminal acceptors of excitationlike P700 and transfer uphill energy to P700. 2.P700+ quenches the LWC fluorescence of PSI trimers and monomers ofA. platensis and Th. elongatus but with different efficiency. 3. LWC740 (F760) in PSI ofA. platensismay correspond to peripherally localized A31/A32/B7trimericaggregate. Localization of LWC719 in PSI of Th. elongatusmay differ since aggregate contains 4 Chls.

  19. 2.Caroteboid-induced NPQ of Phycobilisomes (PBS) fluorescence in cyanobacteria; PBS are the main light-harvesting complex in cyanobacteria Structure of Phycobilisomes, interaction with Photosystems PBS PSII PSI

  20. In 2004 we have found that illumination by blue-green light of Synechocystis cellsquenches the fluoresence of PBSat660 nm; quenching is reversible in dark (Rakhimberdieva et al., FEBS Lett. 2004). =APC dark (non-quenched) after BL (quenched) Action spectrum of quenching Quenching decreases PBSfluorescence at 660 nm (exc. 580 nm)

  21. Photoprotective dissipation of energy in cyanobacteria. 1. PBS is the quenching target, carotenoid is photosensitizer (Rakhimberdieva et al., 2004) 2.Quenching - only at physiological temperatures (Rakhimberdieva et al., 2004, 2007) 3. Quenching is ∆pHindependent (Rakhimberdieva et al., 2006; Wilson et al., 2006) 4.OCP-red (=OCP*) may be fluorescence quencher (Wilson et al., 2006, 2008). Main strategy to reveal the mechanism of quenching - comparison of the activity of PSI and PSII in Synechoystismutant cells innon-quenched andquenched states. PSI activity was measured for PSII-less mutant, PSII activity - for PSI-less mutant. Orange Carotenoid-binding protein (OCP) non-quenched OCP(35 kDa) from A. maxima - two-domain homodimer containing 3’-hydroxiechinenone(Kerfeld et al., 2003) quenched

  22. down regulation of photosynthesis Quantum efficiency of PBS absorption in Synechocystis cellsin quenched state drops by about 40% (P700 photooxidation and PSII fluorescence induction). OCP-triggered energy dissipation in PBS of Synechocystisdivertsexcitation away from both RC (Rakhimberdieva et al., BBA 2010).

  23. 0 NPQ norm. max PSI/PSII-less -1 - 0 WT WT + 620 640 660 680 700 720 740 760 780 Wavelength, nm BL-induced quenchingtakes place even at the absence of PSI and PSII (Rakhimberdieva et al., FEBS Lett. 2011) Fluorescence quenching spectra at 77 K and RT(top) and the second derivative of quenching spectrum at RT(down). 77K fluorescencespectra (exc. 570 nm) ofWT andPSI/PSII-less mutant 77K 288 К 77 К 288 К 680 660

  24. Light saturation curves ofquenching centre formation BL Kuzminov….. Karapetyan BBA 2012

  25. 2. Conclusions on OCP-induced NPQ 1.Carotenoidis photosensitizer of PBS quenching, APC is a target of OCP-induced fluorescence quenching in Synechocystis cells. 2. OCP-induced quenchingof APC fluorescence in Synechocystiscellsdiverts excitation energy from PBS to PSI and PSII reaction centresdecreasingtheenergyflowfromPBS. 3. Excitation of carotenoid in Synechocystisinduces the multistep OCP transformation as sensitizer and as quencher.

  26. Thanks to colleagues Rakhimberdieva M.G. A.N. Bach Institute of Biochemistry RAS, Moscow Shubin V.V. Bolychevtseva Y.V Terekhova I.V. Elanskaya I.V. Biology Faculty, Genetics Dep., MSU Kuzminov F.I. Physics Faculty, Dep. of Non-linear Fluorimetry, MSU Schlodder E. Max-Volmer Laboratorium, Technical University Berlin, Germany Rögner M. Plant Biochemistry Dep., Ruhr-University-Bochum, Germany Vermaas W.F.J. School of Life Sciences, Arizona State University, Tempe, USA

More Related