PGR5 (source code)
= PGR5
{c}
<PGR5> is a thylakoid-associated <protein> implicated in regulation of cyclic electron transport around <photosystem I> in <plants>. Unlike linear electron transport, a cyclic route can contribute to a <proton-motive force> without producing the same net output of reducing equivalents. This helps adjust the balance between <ATP> supply and other photosynthetic demands. <PGR5 is involved in cyclic electron flow around photosystem I and is essential for photoprotection in Arabidopsis by Yuri Munekage and others>[2002, abstract: pgr5 mutant, ferredoxin-to-plastoquinone pathway and proton-gradient regulation]{ref}
The original <Arabidopsis thaliana> mutant failed to downregulate photochemistry normally under intense illumination. The proposed connection was that altered electron-flow regulation weakens the pH difference that supports protective energy dissipation. The genetic result establishes a functional requirement in the pathway; it does not by itself show that isolated <PGR5> is the complete electron-transfer catalyst.
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