The Presence of the IsiA-PSI Supercomplex Leads to Enhanced Photosystem i Electron Throughput in Iron-Starved Cells of Synechococcus sp. PCC 7002

Junlei Sun, John H. Golbeck

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Photosystem I (PS I) is highly demanding of iron, requiring 12 atoms in the bound FX, FB, and FA iron-sulfur clusters and two atoms in the mobile acceptor protein ferredoxin. When grown under iron-limiting conditions, certain cyanobacteria express IsiA, a peripheral chlorophyll a antenna protein, and IsiB, a flavodoxin that substitutes for ferredoxin. The IsiA protein forms single and double rings around PS I, presumably to increase the optical cross-section so as to compensate for fewer PS I complexes. Previous studies have shown that IsiA serves as an efficient light-harvesting structure (Andrizhievskaya, G. G.; et al. Biochim. Biophys. Acta 2002, 1556, 262-272); however, few, if any, studies have been carried out to show that the increased optical cross-section leads to an enhanced rate of electron transfer through PS I. Here, we report a more rapid transient accumulation of the A1 - phyllosemiquinone anion radical by EPR spectroscopy in dark-adapted iron-depleted cells than in iron-replete cells after a block of intense light. A derivative-shaped optical signal in the light-minus-dark difference spectrum of PS I from an electrochromic bandshift of a carotenoid located near the A1 phylloquinones is enhanced in iron-depleted wild-type cells and in an iron-depleted isiB deletion strain, which lacks flavodoxin, but is greatly diminished in an iron-depleted isiA deletion strain, which lacks IsiA and flavodoxin. These findings indicate that the transient accumulation of electrons on A1 occurs more rapidly in the IsiA/PS I supercomplex than in the PS I complex alone. Thus, the increased absorption cross-section from the IsiA proteins translates directly to an enhanced rate of electron transfer through PS I.

Original languageEnglish (US)
Pages (from-to)13549-13559
Number of pages11
JournalJournal of Physical Chemistry B
Volume119
Issue number43
DOIs
StatePublished - Oct 29 2015

Fingerprint

Photosystem I Protein Complex
Iron
Throughput
iron
Electrons
Flavodoxin
cells
electrons
proteins
Proteins
Ferredoxins
deletion
electron transfer
phylloquinone
Vitamin K 1
Atoms
carotenoids
cross sections
chlorophylls
Chlorophyll

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

Cite this

@article{8585bf88cde34e67a4c93fb8460eac64,
title = "The Presence of the IsiA-PSI Supercomplex Leads to Enhanced Photosystem i Electron Throughput in Iron-Starved Cells of Synechococcus sp. PCC 7002",
abstract = "Photosystem I (PS I) is highly demanding of iron, requiring 12 atoms in the bound FX, FB, and FA iron-sulfur clusters and two atoms in the mobile acceptor protein ferredoxin. When grown under iron-limiting conditions, certain cyanobacteria express IsiA, a peripheral chlorophyll a antenna protein, and IsiB, a flavodoxin that substitutes for ferredoxin. The IsiA protein forms single and double rings around PS I, presumably to increase the optical cross-section so as to compensate for fewer PS I complexes. Previous studies have shown that IsiA serves as an efficient light-harvesting structure (Andrizhievskaya, G. G.; et al. Biochim. Biophys. Acta 2002, 1556, 262-272); however, few, if any, studies have been carried out to show that the increased optical cross-section leads to an enhanced rate of electron transfer through PS I. Here, we report a more rapid transient accumulation of the A1 - phyllosemiquinone anion radical by EPR spectroscopy in dark-adapted iron-depleted cells than in iron-replete cells after a block of intense light. A derivative-shaped optical signal in the light-minus-dark difference spectrum of PS I from an electrochromic bandshift of a carotenoid located near the A1 phylloquinones is enhanced in iron-depleted wild-type cells and in an iron-depleted isiB deletion strain, which lacks flavodoxin, but is greatly diminished in an iron-depleted isiA deletion strain, which lacks IsiA and flavodoxin. These findings indicate that the transient accumulation of electrons on A1 occurs more rapidly in the IsiA/PS I supercomplex than in the PS I complex alone. Thus, the increased absorption cross-section from the IsiA proteins translates directly to an enhanced rate of electron transfer through PS I.",
author = "Junlei Sun and Golbeck, {John H.}",
year = "2015",
month = "10",
day = "29",
doi = "10.1021/acs.jpcb.5b02176",
language = "English (US)",
volume = "119",
pages = "13549--13559",
journal = "Journal of Physical Chemistry B Materials",
issn = "1520-6106",
publisher = "American Chemical Society",
number = "43",

}

TY - JOUR

T1 - The Presence of the IsiA-PSI Supercomplex Leads to Enhanced Photosystem i Electron Throughput in Iron-Starved Cells of Synechococcus sp. PCC 7002

AU - Sun, Junlei

AU - Golbeck, John H.

PY - 2015/10/29

Y1 - 2015/10/29

N2 - Photosystem I (PS I) is highly demanding of iron, requiring 12 atoms in the bound FX, FB, and FA iron-sulfur clusters and two atoms in the mobile acceptor protein ferredoxin. When grown under iron-limiting conditions, certain cyanobacteria express IsiA, a peripheral chlorophyll a antenna protein, and IsiB, a flavodoxin that substitutes for ferredoxin. The IsiA protein forms single and double rings around PS I, presumably to increase the optical cross-section so as to compensate for fewer PS I complexes. Previous studies have shown that IsiA serves as an efficient light-harvesting structure (Andrizhievskaya, G. G.; et al. Biochim. Biophys. Acta 2002, 1556, 262-272); however, few, if any, studies have been carried out to show that the increased optical cross-section leads to an enhanced rate of electron transfer through PS I. Here, we report a more rapid transient accumulation of the A1 - phyllosemiquinone anion radical by EPR spectroscopy in dark-adapted iron-depleted cells than in iron-replete cells after a block of intense light. A derivative-shaped optical signal in the light-minus-dark difference spectrum of PS I from an electrochromic bandshift of a carotenoid located near the A1 phylloquinones is enhanced in iron-depleted wild-type cells and in an iron-depleted isiB deletion strain, which lacks flavodoxin, but is greatly diminished in an iron-depleted isiA deletion strain, which lacks IsiA and flavodoxin. These findings indicate that the transient accumulation of electrons on A1 occurs more rapidly in the IsiA/PS I supercomplex than in the PS I complex alone. Thus, the increased absorption cross-section from the IsiA proteins translates directly to an enhanced rate of electron transfer through PS I.

AB - Photosystem I (PS I) is highly demanding of iron, requiring 12 atoms in the bound FX, FB, and FA iron-sulfur clusters and two atoms in the mobile acceptor protein ferredoxin. When grown under iron-limiting conditions, certain cyanobacteria express IsiA, a peripheral chlorophyll a antenna protein, and IsiB, a flavodoxin that substitutes for ferredoxin. The IsiA protein forms single and double rings around PS I, presumably to increase the optical cross-section so as to compensate for fewer PS I complexes. Previous studies have shown that IsiA serves as an efficient light-harvesting structure (Andrizhievskaya, G. G.; et al. Biochim. Biophys. Acta 2002, 1556, 262-272); however, few, if any, studies have been carried out to show that the increased optical cross-section leads to an enhanced rate of electron transfer through PS I. Here, we report a more rapid transient accumulation of the A1 - phyllosemiquinone anion radical by EPR spectroscopy in dark-adapted iron-depleted cells than in iron-replete cells after a block of intense light. A derivative-shaped optical signal in the light-minus-dark difference spectrum of PS I from an electrochromic bandshift of a carotenoid located near the A1 phylloquinones is enhanced in iron-depleted wild-type cells and in an iron-depleted isiB deletion strain, which lacks flavodoxin, but is greatly diminished in an iron-depleted isiA deletion strain, which lacks IsiA and flavodoxin. These findings indicate that the transient accumulation of electrons on A1 occurs more rapidly in the IsiA/PS I supercomplex than in the PS I complex alone. Thus, the increased absorption cross-section from the IsiA proteins translates directly to an enhanced rate of electron transfer through PS I.

UR - http://www.scopus.com/inward/record.url?scp=84946054726&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84946054726&partnerID=8YFLogxK

U2 - 10.1021/acs.jpcb.5b02176

DO - 10.1021/acs.jpcb.5b02176

M3 - Article

C2 - 26046955

AN - SCOPUS:84946054726

VL - 119

SP - 13549

EP - 13559

JO - Journal of Physical Chemistry B Materials

JF - Journal of Physical Chemistry B Materials

SN - 1520-6106

IS - 43

ER -