Data/hora: 02/06/2024 15:58:41

Provedor de dados: 	17	
País: 	United Kingdom	
Título: 	Cationic State Distributions over Chlorophyll Pairs in Photosystem I and II	
Autores: 	Keisuke Saito; Hiroshi Ishikita.	
Data: 	2011-10-03	
Ano: 	2011	
Palavras-chave: 	Chemistry; Bioinformatics; Plant Biology.	
Resumo: 	Photosystem I (PSI) and II (PSII) possess chlorophyll pairs P~A~/P~B~ and P~D1~/P~D2~, respectively. These chlorophylls are the primary electron donors in the light-induced electron transfer. After the electron transfer, the radical cation remains on these chlorophyll pairs, forming [P~A~/P~B~]^&amp;#xb7;+^ and [P~D1~/P~D2~]^&amp;#xb7;+^. The positive charge distributions over the two chlorophylls were reported to be 10/90-50/50 for P~A~^&amp;#xb7;+^/P~B~^&amp;#xb7;+^ [1,2] and 70/30-80/20 for P~D1~^&amp;#xb7;+^/P~D2~^&amp;#xb7;+^ [3,4]. To clarify the origin of the distributions, we calculated ratios of P~A~^&amp;#xb7;+^/P~B~^&amp;#xb7;+^ and P~D1~^&amp;#xb7;+^/P~D2~^&amp;#xb7;+^ with a quantum mechanical/molecular mechanical (QM/MM) approach and the redox potentials (_E_~m~) of monomeric chlorophylls P~A~, P~B~, P~D1~, and P~D2~ with an electrostatic continuum-model approach, using the crystal structures of PSI [5] and PSII [6]. &amp;#xd;&amp;#xa;1) Our QM/MM calculation reproduced the experimentally measured ratios of P~A~^&amp;#xb7;+^/P~B~^&amp;#xb7;+^ [1,2] and P~D1~^&amp;#xb7;+^/P~D2~^&amp;#xb7;+^ [3,4]. The calculated ratios were strongly correlated with the calculated _E_~m~ values. 2) We analyzed residues on puseudo-symmetrical subunit pairs PsaA/PasB and D1/D2 that shifted _E_~m~ of P~A~, P~B~, P~D1~, and P~D2~ and identified the residue pairs responsible for the P~A~^&amp;#xb7;+^/P~B~^&amp;#xb7;+^ and the P~D1~^&amp;#xb7;+^/P~D2~^&amp;#xb7;+^ ratios. In PSII, the difference in the electrostatic protein environments between D1 and D2 was significant in determining the P~D1~^&amp;#xb7;+^/P~D2~^&amp;#xb7;+^ ratio, whereas geometric differences between P~A~ and P~B~ (P~A~ as the C13^2^ epimer of chlorophyll a and the H-bond pattern) played a role in determining the P~A~^&amp;#xb7;+^/P~B~^&amp;#xb7;+^ ratio in PSI.&amp;#xd;&amp;#xa;&amp;#xd;&amp;#xa;References:&amp;#xd;&amp;#xa;[1] A. N. Webber, W. Lupitz, _Biochim. Biophys. Acta. 1507_ (2001)  61.&amp;#xd;&amp;#xa;[2] M. Pantelidou, P. R. Chitnis et al., _Biochemistry 43_ (2004)  8380.&amp;#xd;&amp;#xa;[3] I. H. Davis, P. Heathcote et al., _Biochim. Biophys. Acta. 1143_ (1993)  183.&amp;#xd;&amp;#xa;[4] T. Okubo, T. Tomo et al., _Biochemistry 46_ (2007)  4390.&amp;#xd;&amp;#xa;[5] P. Jordan, P. Fromme et al., _Nature  411_ (2001)  909.&amp;#xd;&amp;#xa;[6] Y. Umena, K. Kawakami et al., _Nature 473_  (2011)   55. &amp;#xd;&amp;#xa;	
Tipo: 	Poster	
Identificador: 	http://precedings.nature.com/documents/6486/version/1

oai:nature.com:10.1038/npre.2011.6486.1

http://dx.doi.org/10.1038/npre.2011.6486.1	
Fonte: 	Nature Precedings	
Fonte: 	Creative Commons Attribution 3.0 License