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. 1980 Oct;66(4):696–703. doi: 10.1104/pp.66.4.696

Further Characterization of the in Vitro Binding of Phytochrome To a Membrane Fraction Enriched for Mitochondria 1

Thomas E Cedel 1,2, Stanley J Roux 1,2
PMCID: PMC440706  PMID: 16661505

Abstract

This study employs 125I-labeled phytochrome (125I-P) from oats to quantitate the binding of phytochrome to a membrane fraction from oats that is highly enriched for mitochondria, and it examines several parameters that influence this attachment. The binding of 125I-Pfr to the mitochondrial fraction of unirradiated oat seedlings is significantly higher than that of 125I-Pr. However, 125I-Pfr and 125I-Pr bind in equal quantities to mitochondrial preparations isolated from light-exposed seedlings. Maximum 125I-Pfr binding to membranes from light-exposed plants occurs within 30 seconds and is optimized in a reaction buffer containing 5 millimolar MgCl2 at pH 6.8. Scatchard plots of the binding data for Pfr indicate a single high-affinity site with an affinity constant of 1.79 × 1011 per molar. When optimal binding conditions are used, over 20% of the 125I-P added is bound and a stoichiometry of about 100 molecules per mitochondrion is attained. When the specificity of binding is tested using competition experiments with a 15-fold excess of unlabeled phytochrome, 125I-Pfr shows no specific binding to rat liver mitochondria.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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