Bald, Dirk

Boekema, Egbert J.

Boonstra, Arjen F.

Kruip, Jochen

Rögner, Matthias

English

An isolation procedure was developed for the cyanobacterium Synechocystis 6803 (and 6714) which yields both monomeric and trimeric photosystem I complexes (P700·FA/FB complexes) depleted of the stroma-exposed subunits PsaC, -D, and -E (P700·FX complexes). Analysis by high resolution gel electrophoresis in combination with immunoblotting and N-terminal sequencing reveals the selective and quantitative removal of PsaC, -D, and -E from the P700·FA/FB complex, containing PsaA, -B, -C, -D, -E, -F, -K, -L and at least two subunits ≤4 kDa. Monomeric and trimeric P700·Fx complexes show an identical subunit composition and an identical charge recombination half-time of 750 ± 250 µs as determined by flash-induced absorption change measurements, reflecting the quantitative loss of iron-sulfur clusters FA/FB and the presence of cluster FX. The existence of a stable trimeric P700·FX complex enables a detailed structural analysis by electron microscopy with high resolution. Comparison of averaged top and side view projections of P700·FX and P700·FA/FB complexes show that the height of the complex is reduced by about 2.5-3.3 nm upon removal of the three stroma-exposed subunits and indicate the position of these three subunits on the PS I surface. While the outer contours of the stroma exposed mass of PS I agree very well with the three-dimensional crystal analysis recently published for trimeric PS I of Synechococcus elongatus, only the structural analysis presented here is able to assign the stroma-exposed mass exclusively to the subunits PsaC, -D, and -E and to exclude a contribution of other subunits

Dissertations of the University of Groningen

Isolation and Structural Characterization of Monomeric and Trimeric Photosystem I Complexes (P700·FA/FB and P700·Fx) from the Cyanobacterium Synechocystis PCC 6803

https://pure.rug.nl/ws/files/14462409/1993JBiolChemKruip.pdf

Isolation and Structural Characterization of Monomeric and Trimeric Photosystem I Complexes (P700·FA/FB and P700·Fx) from the Cyanobacterium Synechocystis PCC 6803

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Dissertations of the University of Groningen