New insights on Chl D1 function in Photosystem II from site-directed mutants of D1/T179 in Thermosynechococcus elongatus.

Autor: Takegawa Y; Graduate School of Science and Technology, Ehime University, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan., Nakamura M; Graduate School of Science and Technology, Ehime University, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan., Nakamura S; Division of Material Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan., Noguchi T; Division of Material Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan., Sellés J; Institut de Biologie Physico-Chimique, UMR CNRS 7141 and Sorbonne Université, 13 rue Pierre et Marie Curie, 75005 Paris, France., Rutherford AW; Department of Life Sciences, Imperial College, London SW7 2AZ, United Kingdom., Boussac A; I(2)BC, UMR CNRS 9198, CEA Saclay, 91191 Gif-sur-Yvette, France. Electronic address: alain.boussac@cea.fr., Sugiura M; Graduate School of Science and Technology, Ehime University, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan; Proteo-Science Research Center, Ehime University, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan. Electronic address: miwa.sugiura@ehime-u.ac.jp.
Jazyk: angličtina
Zdroj: Biochimica et biophysica acta. Bioenergetics [Biochim Biophys Acta Bioenerg] 2019 Apr 01; Vol. 1860 (4), pp. 297-309. Date of Electronic Publication: 2019 Jan 29.
DOI: 10.1016/j.bbabio.2019.01.008
Abstrakt: The monomeric chlorophyll, Chl D1 , which is located between the P D1 P D2 chlorophyll pair and the pheophytin, Pheo D1, is the longest wavelength chlorophyll in the heart of Photosystem II and is thought to be the primary electron donor. Its central Mg 2+ is liganded to a water molecule that is H-bonded to D1/T179. Here, two site-directed mutants, D1/T179H and D1/T179V, were made in the thermophilic cyanobacterium, Thermosynechococcus elongatus, and characterized by a range of biophysical techniques. The Mn 4 CaO 5 cluster in the water-splitting site is fully active in both mutants. Changes in thermoluminescence indicate that i) radiative recombination occurs via the repopulation of *Chl D1 itself; ii) non-radiative charge recombination reactions appeared to be faster in the T179H-PSII; and iii) the properties of P D1 P D2 were unaffected by this mutation, and consequently iv) the immediate precursor state of the radiative excited state is the Chl D1 + Pheo D1 - radical pair. Chlorophyll bleaching due to high intensity illumination correlated with the amount of 1 O 2 generated. Comparison of the bleaching spectra with the electrochromic shifts attributed to Chl D1 upon Q A - formation, indicates that in the T179H-PSII and in the WT*3-PSII, the Chl D1 itself is the chlorophyll that is first damaged by 1 O 2 , whereas in the T179V-PSII a more red chlorophyll is damaged, the identity of which is discussed. Thus, Chl D1 appears to be one of the primary damage site in recombination-mediated photoinhibition. Finally, changes in the absorption of Chl D1 very likely contribute to the well-known electrochromic shifts observed at ~430 nm during the S-state cycle.
(Copyright © 2019. Published by Elsevier B.V.)
Databáze: MEDLINE
Externí odkaz: