Synthesis and characterization of de novo designed peptides modelling the binding sites of [4Fe-4S] clusters in photosystem I.
Photosystem I (PS I) converts the energy of light into chemical energy via transmembrane charge separation. The terminal electron transfer cofactors in PS I are three low-potential [4Fe-4S] clusters named F(X), F(A) and F(B), the last two are bound by the PsaC subunit. We have modelled the F(A) and F(B) binding sites by preparing two apo-peptides (maquettes), sixteen amino acids each. These model peptides incorporate the consensus [4Fe-4S] binding motif along with amino acids from the immediate environment of the iron-sulfur clusters F(A) and F(B). The [4Fe-4S] clusters were successfully incorporated into these model peptides, as shown by optical absorbance, EPR and Mössbauer spectroscopies. The oxidation-reduction potential of the iron-sulfur cluster in the F(A)-maquette is -0.44+/-0.03 V and in the F(B)-maquette is -0.47+/-0.03 V. Both are close to that of F(A) and F(B) in PS I and are considerably more negative than that observed for other [4Fe-4S] model systems described earlier (Gibney, B. R., Mulholland, S. E., Rabanal, F., and Dutton, P. L. Proc. Natl. Acad. Sci. U.S.A. 93 (1996) 15041-15046). Our optical data show that both maquettes can irreversibly bind to PS I complexes, where PsaC-bound F(A) and F(B) were removed, and possibly participate in the light-induced electron transfer reaction in PS I.
Antonkine
Mikhail L
ML
Max-Planck-Institut für Bioanorganische Chemie, Stiftstr. 34-36, D-45470 Mülheim an der Ruhr, Germany. antonkin@mpi-muelheim.mpg.de
Koay
Melissa S
MS
Epel
Boris
B
Breitenstein
Christoph
C
Gopta
Oxana
O
Gärtner
Wolfgang
W
Bill
Eckhard
E
Lubitz
Wolfgang
W
D000595:Amino Acid Sequence; D001059:Apoproteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D002734:Chlorophyll / Q000737:chemistry / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D045331:Photosystem I Protein Complex / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D015204:Spectroscopy, Mossbauer
D001059:Apoproteins; D007506:Iron-Sulfur Proteins; D010455:Peptides; D045331:Photosystem I Protein Complex; C089909:photosystem I, psaB subunit; D002734:Chlorophyll; C001785:chlorophyll P 700