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Introduction of a [4Fe-4S (S-cys)4]+1,+2 iron-sulfur center into a four-α helix protein using design parameters from the domain of the Fx cluster in the Photosystem I reaction center
Protein Science
  • Marvin Paul Scott, United States Department of Agriculture
  • John Biggins, Brown University
Document Type
Article
Publication Version
Published Version
Publication Date
2-1-1997
DOI
10.1002/pro.5560060209
Abstract

We describe the insertion of an iron-sulfur center into a designed four α-helix model protein. The model protein was re-engineered by introducing four cysteine ligands required for the coordination of the mulinucleate cluster into positions in the main-chain directly analogous to the domain predicted to ligand the interpeptide [4Fe-4S (S-cys)4] cluster, Fx, from PsaA and PsaB of the Photosystem I reaction center. This was achieved by inserting the sequence, CDGPGRGGTC, which is conserved in PsaA and PsaB, into interhelical loops 1 and 3 of the four α-helix model. The holoprotein was characterized spectroscopically after insertion of the iron-sulfur center in vitro. EPR spectra confirmed the cluster is a [4Fe-4S] type, indicating that the cysteine thiolate ligands were positioned as designed. The midpoint potential of the iron-sulfur center in the model holoprotein was determined via redox titration and shown to be −422 mV (pH 8.3,n = 1). The results support proposals advanced for the structure of the domain of the [4Fe-4S] Fx cluster in Photosystem I based upon sequence predictions and molecular modeling. We suggest that the lower potential of the Fx cluster is most likely due to factors in the protein environment of Fx rather than the identity of the residues proximal to the coordinating ligands.

Comments

This article is from Protein Science 6 (1997): 340, doi:10.1002/pro.5560060209.

Rights
Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted.
Language
en
File Format
application/pdf
Citation Information
Marvin Paul Scott and John Biggins. "Introduction of a [4Fe-4S (S-cys)4]+1,+2 iron-sulfur center into a four-α helix protein using design parameters from the domain of the Fx cluster in the Photosystem I reaction center" Protein Science Vol. 6 Iss. 2 (1997) p. 340 - 346
Available at: http://works.bepress.com/paul-scott/19/