These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Assembly of protein subunits within the stromal ridge of photosystem I. Structural changes between unbound and sequentially PS I-bound polypeptides and correlated changes of the magnetic properties of the terminal iron sulfur clusters.
    Author: Antonkine ML, Jordan P, Fromme P, Krauss N, Golbeck JH, Stehlik D.
    Journal: J Mol Biol; 2003 Mar 28; 327(3):671-97. PubMed ID: 12634061.
    Abstract:
    The X-ray structure of Photosystem I (PS I) from Synechococcus elongatus was recently solved at 2.5A resolution (PDB entry 1JB0). It provides a structural model for the stromal subunits PsaC, PsaD and PsaE, which comprise the "stromal ridge" of PS I. In a separate set of studies the three-dimensional solution structures of the unbound, recombinant PsaC (PDB entry 1K0T) and PsaE (PDB entries 1PSF, 1QP2 and 1GXI) subunits were solved by NMR. The PsaC subunit of PS I is a small (9.3 kDa) protein that harbors binding sites for two [4Fe-4S] clusters F(A) and F(B), which are the terminal electron acceptors in PS I. Comparison of the PsaC structure in solution with that in the X-ray structure of PS I reveals significant differences between them which are summarized and evaluated here. Changes in the magnetic properties of [4Fe-4S] centers F(A) and F(B) are related to changes in the protein structure of PsaC, and they are further influenced by the presence of PsaD. Based on experimental evidence, three assembly stages are analyzed: PsaC(free), PsaC(only), PsaC(PS I). Unbound, recombinant PsaD, studied by NMR, has only a few elements of secondary structure and no stable three-dimensional structure in solution. When PsaD is bound in PS I, it has a well-defined three-dimensional structure. For PsaE the three-dimensional structure is very similar in solution and in the PS I-bound form, with the exception of two loop regions. We suggest that the changes in the structures of PsaC and PsaD are caused by the sequential formation of multiple networks of contacts between the polypeptides of the stromal ridge and between those polypeptides and the PsaA/PsaB core polypeptides. The three-dimensional structure of the C(2)-symmetric F(X)-binding loops on PsaA and PsaB were also analyzed and found to be significantly different from the binding sites of other proteins that contain interpolypeptide [4Fe-4S] clusters. The aim of this work is to relate contact information to structural changes in the proteins and to propose a model for the assembly of the stromal ridge of PS I based on this analysis.
    [Abstract] [Full Text] [Related] [New Search]