Solution NMR structure and backbone dynamics of the PsaE subunit of photosystem I from Synechocystis sp. PCC 6803.
PsaE is a small peripheral subunit of photosystem I (PSI) that is very accessible to the surrounding medium. It plays an essential role in optimizing the interactions with the soluble electron acceptors of PSI, ferredoxin and flavodoxin. The solution structure of PsaE from the cyanobacterium Synechocystis sp. PCC 6803 has been investigated by NMR with a special emphasis on its protein dynamic properties. PsaE is characterized by a well-defined central core that consists of a five-stranded beta-sheet (+1, +1, +1, -4x). Four loops (designated the A-B, B-C, C-D, and D-E loops) connect these beta-strands, the overall resulting structure being that of an SH3-like domain. As compared to previously determined PsaE structures, conformational differences are observed in the first three loops. The flexibility of the loops was investigated using (15)N relaxation experiments. This flexibility is small in amplitude for the A-B and B-C loops, but is large for the C-D loop, particularly in the region corresponding to the missing sequence of Nostoc sp. PCC 8009. The plasticity of the connecting loops in the free subunit is compared to that when bound to the PSI and discussed in relation to the insertion process and the function(s) of PsaE.
Barth
Patrick
P
Département de Biologie Joliot Curie, Service de Bioénergétique, CEA de Saclay and URA CNRS 2096, F-91191 Gif sur Yvette Cedex, France.
Savarin
Philippe
P
Gilquin
Bernard
B
Lagoutte
Bernard
B
Ochsenbein
Françoise
F
D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D000458:Cyanobacteria / Q000737:chemistry*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry*; D045331:Photosystem I Protein Complex; D017433:Protein Structure, Secondary; D021122:Protein Subunits / Q000737:chemistry; D011994:Recombinant Proteins / Q000737:chemistry; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D021122:Protein Subunits; D011994:Recombinant Proteins; C079741:photosystem I, psaE subunit