Open Reading Frame ssr2016 is Required for Antimycin A-sensitive Photosystem I-driven Cyclic Electron Flow in the Cyanobacterium Synechocystis sp. PCC 6803

ABSTRACT Open reading frame sll1556 in the cyanobacterium Synechocystis sp. strain 6803 encodes a putative type II isopentenyl diphosphate (IPP) isomerase. The His6-tagged protein was produced in Escherichia coli and purified by Ni2+ chromatography. The homotetrameric enzyme required NADPH, flavin mononucleotide, and Mg2+ for activity; K m IPP was 52 μM, and k cat IPP was 0.23 s−1.

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Electron Flow from NAD(P)H Dehydrogenase to Photosystem I is Required for Adaptation to Salt Shock in the Cyanobacterium Synechocystis sp. PCC 6803

Plant and Cell Physiology ◽

10.1093/oxfordjournals.pcp.a029123 ◽

1997 ◽

Vol 38 (12) ◽

pp. 1311-1318 ◽

Cited By ~ 37

Author(s):

Y. Tanaka ◽

S. Katada ◽

H. Ishikawa ◽

T. Ogawa ◽

T. Takabe

Keyword(s):

Photosystem I ◽

Electron Flow ◽

Salt Shock ◽

Synechocystis Sp ◽

Pcc 6803

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PGRL2 triggers degradation of PGR5 in the absence of PGRL1

Nature Communications ◽

10.1038/s41467-021-24107-7 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Thilo Rühle ◽

Marcel Dann ◽

Bennet Reiter ◽

Danja Schünemann ◽

Belen Naranjo ◽

...

Keyword(s):

Plant Growth ◽

Photosystem I ◽

Electron Flow ◽

Cyclic Electron Flow ◽

Antimycin A ◽

Thylakoid Proteins ◽

Redox Active ◽

Distant Homolog

AbstractIn plants, inactivation of either of the thylakoid proteins PGR5 and PGRL1 impairs cyclic electron flow (CEF) around photosystem I. Because PGR5 is unstable in the absence of the redox-active PGRL1, but not vice versa, PGRL1 is thought to be essential for CEF. However, we show here that inactivation of PGRL2, a distant homolog of PGRL1, relieves the need for PGRL1 itself. Conversely, high levels of PGRL2 destabilize PGR5 even when PGRL1 is present. In the absence of both PGRL1 and PGRL2, PGR5 alters thylakoid electron flow and impairs plant growth. Consequently, PGR5 can operate in CEF on its own, and is the target of the CEF inhibitor antimycin A, but its activity must be modulated by PGRL1. We conclude that PGRL1 channels PGR5 activity, and that PGRL2 triggers the degradation of PGR5 when the latter cannot productively interact with PGRL1.

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The Synechocystis sp. PCC 6803 open reading frame slr0201 that is homologous to sdhC from Archaea codes for a [2Fe-2S] protein

10.1101/2021.09.23.461530 ◽

2021 ◽

Author(s):

Fusheng Xiong ◽

Russell LoBrutto ◽

Wim F. J. Vermaas

Keyword(s):

Sequence Similarity ◽

Immunoblot Analysis ◽

Open Reading Frame ◽

Heterodisulfide Reductase ◽

Redox Titration ◽

High Sequence Similarity ◽

Reading Frame ◽

Midpoint Potential ◽

Synechocystis Sp ◽

Pcc 6803

A hypothetical protein encoded by Synechocystis sp. PCC 6803 open reading frame slr0201 shows high sequence similarity to the C subunit of a group of unusual succinate dehydrogenases found in some archaeal species. Slr0201 was originally annotated as HdrB, the B subunit of heterodisulfide reductase, but appears to be SdhC instead. This protein was overexpressed in E. coli by cloning the PCR-derived slr0201 open reading frame into a pET16b-based expression vector. The overproduced Slr0201 accumulated predominantly in inclusion bodies with an apparent molecular mass of 33 kDa. The protein contained at least one [2Fe-2S] cluster based on UV-visible absorbance and CD spectra and EPR spectroscopy, in conjunction with stoichiometric analysis of protein-bound iron and sulfur content. Redox titration showed a midpoint potential (Em) of + 17 mV at pH 7.0, which is consistent with Slr0201 serving a role in transferring electrons between succinate and plastoquinone. Slr0201 was also overproduced in Synechocystis sp. PCC 6803 by introducing an additional, His-tagged slr0201 into the Synechocystis genome replacing psbA3, creating the slr0201+-His overexpression strain. Immunoblot analysis shows that Slr0201 is membrane-associated in the wild type. However, in the Slr0201+-His strain, immunoreaction occurred in both the membrane and soluble fractions, possibly as a consequence of processing near the N-terminus. The results obtained with Slr0201 are discussed in the light of one of the cyanobacterial SdhB subunits, which shares redox commonalities with archaeal SdhB.

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