Role of acidic amino acid residues of PsaD subunit on limiting the affinity of photosystem I for ferredoxin.
The PsaD subunit of photosystem I is one of the central polypeptides for the interaction with ferredoxin, its acidic electron acceptor. In the cyanobacterium Synechocystis 6803, this role is partly performed by a sequence extending approximately from histidine 97 to arginine 119, close to the C-terminus. In the present work, acidic amino acids D100, E105, and E109 are shown to moderate the affinity of Photosystem I for ferredoxin. Most single replacements of these residues by neutral amino acids increased the affinity for ferredoxin, resulting in a dissociation constant as low as 0.015 microM for the E105Q mutant (wild-type K(D) = 0.4 microM). This is the first report on the limitation of photosystem I affinity for ferredoxin due to acidic amino acids from PsaD subunit. It highlights the occurrence of a negative control on the binding during the formation of transient complexes between electron carriers.
Bottin
H
H
Département de Biologie Cellulaire et Moléculaire, Service de Bioénergétique, CEA, CNRS URA 2096, CE de Saclay, 91191 Gif sur Yvette Cedex, France. bottin@dsvidf.cea.fr
Hanley
J
J
Lagoutte
B
B
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000458:Cyanobacteria / Q000737:chemistry* / Q000235:genetics; D005288:Ferredoxins / Q000378:metabolism*; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry*; D045331:Photosystem I Protein Complex; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding
D001426:Bacterial Proteins; D005288:Ferredoxins; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D010940:Plant Proteins; C070290:PsaD protein, cyanobacteria