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The PsaC subunit of photosystem I provides an essential lysine residue for fast electron transfer to ferredoxin.
- Source :
- EMBO Journal; 2/15/98, Vol. 17 Issue 4, p849-858, 10p
- Publication Year :
- 1998
-
Abstract
- PsaC is the stromal subunit of photosystem I (PSI) which binds the two terminal electron acceptors F<subscript>A</subscript> and F<subscript>B</subscript>. This subunit resembles 2[4Fe-4S] bacterial ferredoxins but contains two additional sequences: an internal loop and a C-terminal extension. To gain new insights into the function of the internal loop, we used an in vivo degenerate oligonucleotide-directed mutagenesis approach for analysing this region in the green alga Chlamydomonas reinhardtii. Analysis of several psaC mutants affected in PSI function or assembly revealed that K<subscript>35</subscript> is a main interaction site between PsaC and ferredoxin (Fd) and that it plays a key role in the electrostatic interaction between Fd and PSI. This is based upon the observation that the mutations K<subscript>35</subscript>T, K<subscript>35</subscript>D and K<subscript>35</subscript>E drastically affect electron transfer from PSI to Fd, as measured by flash-absorption spectroscopy, whereas the K<subscript>35</subscript>R change has no effect on Fd reduction. Chemical cross-linking experiments show that Fd interacts not only with PsaD and PsaE, but also with the PsaC subunit of PSI. Replacement of K<subscript>35</subscript> by T, D, E or R abolishes Fd cross-linking to PsaC, and cross-linking to PsaD and PsaE is reduced in the K<subscript>35</subscript>T, K<subscript>35</subscript>D and K<subscript>35</subscript>E mutants. In contrast, replacement of any other lysine of PsaC does not alter the cross-linking pattern, thus indicating that K<subscript>35</subscript> is an interaction site between PsaC and its redox partner Fd. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 02614189
- Volume :
- 17
- Issue :
- 4
- Database :
- Complementary Index
- Journal :
- EMBO Journal
- Publication Type :
- Academic Journal
- Accession number :
- 13006038
- Full Text :
- https://doi.org/10.1093/emboj/17.4.849