Is the 9 kDa thylakoid membrane phosphoprotein functionally and structurally analogous to the ‘H’ subunit of bacterial reaction centres?

FEBS Letters

Packham, Nigel K.¹ 

[1] Department of Biochemistry, The University, Newcastle-upon-Tyne NE2 4HH, England

关键词: Thylakoid membrane;    Protein phosphorylation;    9 kDa phosphoprotein;    Photosystem II;    Reaction center;    Plastoquinone;    (Bacterium);    PS II;    photosystem II;    D1 and D2;    the two reaction centre subunits of PS II;    L;    M and H;    the light;    medium and heavy subunits of the reaction centre from photosynthetic eubacteria;    QA and QB;    the primary and secondary plastoquinone-binding sites of PS II reaction centres;   

DOI  :  10.1016/0014-5793(88)80835-4

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Although the amino acid sequence of the 9 kDa (phospho)protein of chloroplasts has been determined, the function of this thylakoid membrane protein in photosynthetic electron transport and the reason for its physiological control remains unclear. In this paper, I briefly review the evidence which indicates that the phosphorylation of the 9 kDa protein results in a partial inhibition of photosynthetic oxygen evolution by increasing the stability of the semiquinone bound to Q_A the primary, plastoquinone-binding site of photosystem II (PS II). I propose that in its dephosphorylated state, the 9 kDa thylakoid membrane protein may serve PS II to ensure efficient photochemical charge separation by aiding the transfer of reducing equivalents out of the reaction centre to the attendant plastoquinone pool. This function is analogous to that proposed for the H-subunit of the reaction centre of photosynthetic eubacteria. Whether these two proteins have evolved from a common ancestral reaction centre protein is discussed in the light of a comparison of their amino acid sequences and predicted secondary structures.

【 授权许可】

Unknown