Resolution and reconstitution of the cyanobacterial photosystem I complex

Parrett, Kevin G.; Mehari, Tetemke; Golbeck, John H.

doi:10.1016/0005-2728(90)90039-7

Cited by 76 publications

(56 citation statements)

References 41 publications

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“…Reconstitution of iron-sulfur clusters in PS I core preparation and in the PS I complexes from the PsaC-deficient mutant strains was adapted from the previously reported studies (47,48). Essentially PS I core preparations in the absence or the presence of the isolated small subunits obtained from urea dissociation were suspended in N 2 -purged solutions 0.5% ␤Ϫmercaptoethanol to which FeCl 3 and Na 2 S solutions were added and incubated for 12-18 h. The solution was concentrated to near dryness by ultrafiltration, washed twice with a solution containing 0.05% ␤-mercaptoethanol.…”

Section: Methodsmentioning

confidence: 99%

“…Isolation and Reconstitution of the PS I Core Complexes and the Subunits saC, PsaD, and PsaE-Preparation of PS I core and isolation of subunits PsaC, PsaD, and PsaE were carried out essentially according to the methods as described (47,48). PS I was dissociated by treatment with 6.8 M urea for 10 -30 min until the P700ϩ reduction reached t1 ⁄2 of 1 ms.…”

Section: Methodsmentioning

confidence: 99%

“…To find out whether F X was potentially functional, the clusters F A /F B were reconstituted in the PS I complexes from the PsaC-deficient mutants and in the core preparation. For reconstitution of F A /F B , the F A /F B -binding subunit PsaC and subunits PsaD and PsaE were mixed with the P700-F X -containing complexes in the presence of ␤-mercaptoethanol, Fe 3ϩ , and S 2Ϫ as described previously (47,48,58). The kinetics of P700 ϩ reduction at 820 or 700 nm were measured to evaluate the function of F X in the reconstituted PS I.…”

Section: In Different Ps I Preparationsmentioning

confidence: 99%

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Control of Electron Transport in Photosystem I by the Iron-Sulfur Cluster FX in Response to Intra- and Intersubunit Interactions

Gong

Agalarov

Brettel

et al. 2003

Journal of Biological Chemistry

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Photosystem I (PS I) is a transmembraneal multisubunit complex that mediates light-induced electron transfer from plactocyanine to ferredoxin. The electron transfer proceeds from an excited chlorophyll a dimer (P700) through a chlorophyll a (A 0 ), a phylloquinone (A 1 ), and a [4Fe-4S] iron-sulfur cluster F X , all located on the core subunits PsaA and PsaB, to iron-sulfur clusters F A and F B , located on subunit PsaC. Earlier, it was attempted to determine the function of F X in the absence of F A/B mainly by chemical dissociation of subunit PsaC. However, not all PsaC subunits could be removed from the PS I preparations by this procedure without partially damaging F X . We therefore removed subunit PsaC by interruption of the psaC2 gene of PS I in the cyanobacterium Synechocystis sp. PCC 6803. Cells could not grow under photosynthetic conditions when subunit PsaC was deleted, yet the PsaC-deficient mutant cells grew under heterotrophic conditions and assembled the core subunits of PS I in which light-induced electron transfer from P700 to A 1 occurred. The photoreduction of F X was largely inhibited, as seen from direct measurement of the extent of electron transfer from A 1 to F X . From the crystal structure it can be seen that the removal of subunits PsaC, PsaD, and PsaE in the PsaCdeficient mutant resulted in the braking of salt bridges between these subunits and PsaB and PsaA and the formation of a net of two negative surface charges on PsaA/B. The potential induced on F X by these surface charges is proposed to inhibit electron transport from the quinone. In the complete PS I complex, replacement of a cysteine ligand of F X by serine in site-directed mutation C565S/D566E in subunit PsaB caused an ϳ10-fold slow down of electron transfer from the quinone to F X without much affecting the extent of this electron transfer compared with wild type. Based on these and other results, we propose that F X might have a major role in controlling electron transfer through PS I.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: In Different Ps I Preparationsmentioning

confidence: 99%

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Control of Electron Transport in Photosystem I by the Iron-Sulfur Cluster FX in Response to Intra- and Intersubunit Interactions

Gong

Agalarov

Brettel

et al. 2003

Journal of Biological Chemistry

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“…PSI-C⌬L is unable to accept electrons from F X when PSI-D is not present. However, when the C-terminal extension of this mutant was replaced with the loop sequence, (33), and the samples were desalted anaerobically. Difference spectra of the proteins were recorded as described previously (26).…”

Section: Discussionmentioning

confidence: 99%

The Eight-amino Acid Internal Loop of PSI-C Mediates Association of Low Molecular Mass Iron-Sulfur Proteins with the P700-FXCore in Photosystem I

Naver¹,

Scott²,

Golbeck³

et al. 1998

Journal of Biological Chemistry

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“…The PSI complex of Syneckococcus sp. PCC 6301 is widely used in structural and functional studies of the FA and FB ironsulfur clusters (Parrett et al, 1990).…”

mentioning

confidence: 99%