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Unexpected diversity of ferredoxin-dependent thioredoxin reductases in cyanobacteria

DOI: 10.1093/plphys/kiab072 DOI Help

Authors: Ruben M. Buey (Universidad de Salamanca) , David Fernandez-Justel (Universidad de Salamanca) , Gloria González-Holgado (Instituto de Recursos Naturales y Agrobiología de Salamanca (IRNASA-CSIC)) , Marta Martinez-Julvez (Universidad de Zaragoza) , Adrián González-López (Instituto de Recursos Naturales y Agrobiología de Salamanca (IRNASA-CSIC)) , Adrián Velázquez-Campoy (Universidad de Zaragoza; Aragon Institute for Health Research; Biomedical Research Networking Center in Digestive and Hepatic Diseases (CIBERehd); Fundación ARAID, Government of Aragon) , Milagros Medina (Universidad de Zaragoza) , Bob B. Buchanan (Biomedical Research Networking Center in Digestive and Hepatic Diseases (CIBERehd)) , Monica Balsera (Instituto de Recursos Naturales y Agrobiología de Salamanca (IRNASA-CSIC))
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Plant Physiology

State: Published (Approved)
Published: February 2021
Diamond Proposal Number(s): 20229

Open Access Open Access

Abstract: Thioredoxin reductases control the redox state of thioredoxins (Trxs)—ubiquitous proteins that regulate a spectrum of enzymes by dithiol-disulfide exchange reactions. In most organisms, Trx is reduced by NADPH via a thioredoxin reductase flavoenzyme (NTR), but in oxygenic photosynthetic organisms, this function can also be performed by an iron-sulfur ferredoxin (Fdx)-dependent thioredoxin reductase (FTR) that links light to metabolic regulation. We have recently found that some cyanobacteria, such as the thylakoid-less Gloeobacter and the ocean-dwelling green oxyphotobacterium Prochlorococcus, lack NTR and FTR but contain a thioredoxin reductase flavoenzyme (formerly tentatively called deeply-rooted thioredoxin reductase or DTR), whose electron donor remained undefined. Here we demonstrate that Fdx functions in this capacity and report the crystallographic structure of the transient complex between the plant-type Fdx1 and the thioredoxin reductase flavoenzyme from Gloeobacter violaceus. Thereby, our data demonstrate that this cyanobacterial enzyme belongs to the Fdx flavin-thioredoxin reductase (FFTR) family, originally described in the anaerobic bacterium Clostridium pasteurianum. Accordingly, the enzyme hitherto termed DTR is renamed FFTR. Our experiments further show that the redox sensitive peptide CP12 is modulated in vitro by the FFTR/Trx system, demonstrating that FFTR functionally substitutes for FTR in light-linked enzyme regulation in Gloeobacter. Altogether, we demonstrate the FFTR is spread within the cyanobacteria phylum and propose that, by substituting for FTR, it connects the reduction of target proteins to photosynthesis. Besides, the results indicate that FFTR acquisition constitutes a mechanism of evolutionary adaptation in marine phytoplankton such as Prochlorococcus that live in low-iron environments.

Journal Keywords: NTR; FFTR; ferredoxin; thioredoxin; photosynthesis; cyanobacteria; disulfide; CP12

Diamond Keywords: Cyanobacteria; Enzymes; Photosynthesis

Subject Areas: Biology and Bio-materials, Chemistry

Instruments: B21-High Throughput SAXS , I04-1-Macromolecular Crystallography (fixed wavelength)

Other Facilities: ALBA

Added On: 23/02/2021 09:28


Discipline Tags:

Evolutionary science Biochemistry Catalysis Chemistry Structural biology Life Sciences & Biotech

Technical Tags:

Diffraction Scattering Macromolecular Crystallography (MX) Small Angle X-ray Scattering (SAXS)