Activities of two dissimilar thioredoxins from the cyanobacterium Anabaena sp. strain PCC 7120

Gleason, Florence K.

doi:10.1128/jb.174.8.2592-2598.1992

Cited by 17 publications

(15 citation statements)

References 35 publications

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“…It is thus possible that the thioredoxin diversity observed in cyanobacteria is connected with a need for redox regulating fructose-l,6-bisphosphatase in those organisms which perform oxygenic photosynthesis (this is not true for some other enzymes such as the y subunit of CFl that becomes redox regulatory only in green algae, see later V.l(t^)). The cyanobacterial FBPase-linked thioredoxin is, however, quite different from the higher plant thioredoxin /, being also reduced by glutathione (Gleason, 1992). Sequence analysis implies that the cyanobacterial thioredoxins able to activate fructose-1,6-bisphosphatase do not belong to the eukaryotic/ group.…”

Section: Photosynthetic Organisms (A) Chloroplastic Systemsmentioning

confidence: 97%

Thioredoxins: structure and function in plant cells

1997

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SUMMARY Thioredoxins are ubiquitous small‐molecular‐weight proteins (typically 100–120 amino‐acid residues) containing an extremely reactive disulphide bridge with a highly conserved sequence ‐Cys‐Gly(Ala/Pro)‐Pro‐Cys‐. In bacteria and animal cells, thioredoxins participate in multiple reactions which require reduction of disulphide bonds on selected target proteins/ enzymes. There is now ample biochemical evidence that thioredoxins exert very specific functions in plants, the best documented being the redox regulation of chloroplast enzymes. Another area in which thioredoxins are believed to play a prominent role is in reserve protein mobilization during the process of germination. It has been discovered that thioredoxins constitute a large multigene family in plants with different‐subcellular localizations, a unique feature in living cells so far. Evolutionary studies based on these molecules will be discussed, as well as the available biochemical and genetic evidence related to their functions in plant cells. Eukaryotic photosynthetic plant cells are also unique in that they possess two different reducing systems, one extrachloroplastic dependent on NADPH as an electron donor, and the other one chloroplastic, dependent on photoreduced ferredoxin. This review will examine in detail the latest progresses in the area of thioredoxin structural biology in plants, this protein being an excellent model for this purpose. The structural features of the reducing enzymes ferredoxin thioredoxin reductase and NADPH thioredoxin reductase will also be described. The properties of the target enzymes known so far in plants will be detailed with special emphasis on the structural features which make them redox regulatory. Based on sequence analysis, evidence will be presented that redox regulation of enzymes of the biosynthetic pathways first appeared in cyanobacteria possibly as a way to cope with the oxidants produced by oxygenic photosynthesis. It became more elaborate in the chloroplasts of higher plants where a co‐ordinated functioning of the chloroplastic and extra chloroplastic metabolisms is required.

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Section: Photosynthetic Organisms (A) Chloroplastic Systemsmentioning

confidence: 97%

Thioredoxins: structure and function in plant cells

1997

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“…A third cysteinyl residue is present in the structure, close to the active site, Such a thiol should be able to form intermolecular disulfide bonds, as reported for thioredoxin T2 from Anabacna [54], and for thioredoxin from Dictyostelium discnideum [59]. A dimeric form of Aspergillus thioredoxin, probably resulting from the formation of inter-molecular disulfide bond, was actually observed by electrospray mass spectrometry experiments (8% of the abundance of the monomeric form, see Fig.…”

Section: Discusslonmentioning

confidence: 89%

“…Activation of NADP-MDH usually represents a valuable test ~ fast and sensitive ~ to screen for the presence of thioredoxins, since this enzyme has been reported to be easily activated by non-chloroplastic thioredoxins [20,31,53,541. Moreover, several proteins, first identified as thioredoxins and which were not able to activate NADP-MDH, were recently shown to be more related to glutaredoxins than to thioredoxins [54,551. Using this test, only one thioredoxin was detected and purified from A .…”

Section: Discusslonmentioning

confidence: 99%

Purification, properties and primary structure of thioredoxin from Aspergillus nidulans

Maréchal

Hoang

Schmitter

et al. 1992

European Journal of Biochemistry

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This paper reports the purification and the properties of a thioredoxin from the fungus Aspergillus nidulans. This thioredoxin is an acidic protein which exhibits an unusual fluorescence emission spectrum. characterized by a high contribution of tyrosine residues. Thioredoxin from A . nidulans cannot serve as a substrate for Escherichia coli thioredoxin reductase. Corn NADP-malate dehydrogenase is activated by this thioredoxin in the presence of dithiothreitol, while fructose-I ,6-bisphosphatase is not. The amino acid sequence of Aspergillus thioredoxin was determined by automated Edman degradation after cleavage with trypsin, SV, protease, chymotrypsin and cyanogen bromide. The masses of tryptic peptides were verified by plasma-desorption mass spectrometry. The mass of the protein was determined by electrospray mass spectrometry and shown to be in agreement with the calculated mass derived from the sequence ( M , = 11 564). Compared to thioredoxins from other sources, the protein from A . niduluns displays a maximal sequence similarity with that from yeast (45%).Thioredoxins are a group of small heat-stable proteins found in numerous organisms. They are structurally characterized by a redox active site exhibiting the well-conserved sequence -Trp-Cys-Gly-Pro-Cys- [I]. Thioredoxin was first identified in Escherichia coli where it can serve as a reducing agent for different reductases, involved in the reduction of ribonucleotide [2], sulfate [3] and methionine sulfoxide [4]. The oxidized form of thioredoxin is reduced by a specific NADPH-dependent reductase [5].In higher plants, thioredoxins are involved in the modulation ofenzymic activities by thiol redox control, during light: dark transitions [6]. Three different thioredoxins have been purified from spinach leaves and characterized; two, located in the chloroplast, regulate the activity of target enzymes such as NADP-malate dehydrogenase, (m-type thioredoxin) and fmctose-l,6-bisphosphatase (f-type thioredoxin) [7], by reducing disulfide bonds. These chloroplast thioredoxins are reduced by a specific ferredoxin-thioredoxin reductase [8]. The third thioredoxin, called thioredoxin h [9] was purified from other compartments of the cell (mitochondria, cytosol, endoplasmic reticulum) [lo]. It has been assigned a physiological function only in seeds, where it reduces cystine-rich proteins, such as purothionin, a-amylase and trypsin inhibitors [ll].

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“…All of these critical motifs, along with a PDO-like pattern of hydrophobic residues, are found in the thioredoxin-like domain of TxlA. Since TxlA differs in several residues around the active site that are highly conserved among the thioredoxins and is larger than most thioredoxins (although unusually large cyanobacterial ''thioredoxins'' have been reported [31]), TxlA is unlikely to be a true thioredoxin. Instead, TxlA may function more like the PDIs, which facilitate proper polypeptide folding in the endoplasmic reticulum of eukaryotes and the periplasmic space of bacteria (2,8,9,35,50,59), or like a related group of PDOs involved in cytochrome biosynthesis in the periplasm of bacteria (10,39).…”

Section: Discussionmentioning

confidence: 99%

Disruption of a gene encoding a novel thioredoxin-like protein alters the cyanobacterial photosynthetic apparatus

Collier

Grossman

1995

J Bacteriol

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A gene that may encode a novel protein disulfide oxidoreductase, designated txlA (thioredoxin-like), was isolated from the cyanobacterium Synechococcus sp. strain PCC7942. Interruption of txlA near the putative thioredoxin-like active site yielded cells that grew too poorly to be analyzed. In contrast, a disruption of txlA near the C terminus that left the thioredoxin-like domain intact yielded two different mutant phenotypes. One type, designated txlXb, exhibited a slightly reduced growth rate and an increased cellular content of apparently normal phycobilisomes. The cellular content of phycobilisomes also increased in the other mutant strain, designated txlXg. However, txlXg also exhibited a proportionate increase in chlorophyll and other components of the photosynthetic apparatus and grew as fast as wild-type cells. Both the txlXb and txlXg phenotypes were stable. The differences between the two strains may result from a genetic polymorphism extant in the original cell population. Further investigation of txlA may provide new insights into mechanisms that regulate the structure and function of the cyanobacterial photosynthetic apparatus.The conversion of light energy into chemical energy (ATP) and reducing power (NADPH) by oxygen-evolving photosynthetic organisms requires the coordinated activity of photosystem I (PSI) and photosystem II (PSII), along with their lightharvesting antenna pigments and intermediary electron transport components. NADPH is produced only by linear electron flow through both PSII and PSI, but ATP can be produced either by linear electron flow or by cyclic electron flow around PSI alone (24, 34). In cyanobacteria, PSI is excited almost entirely by light absorbed by chlorophyll a (Chl; A max , 440 and 680 nm), while PSII receives most of its excitation energy from light absorbed by the phycobilisomes (PBS; A max , 560 to 620 nm [32]). Within these basic functional constraints, the structure of the photosynthetic apparatus is dynamic. For example, while the PBS-to-Chl ratio generally reflects the PSII-to-PSI ratio, under some conditions cyanobacteria can modulate the light-harvesting capacity of PBS relative to Chl independently of the PSII-to-PSI ratio by changing the size of the PBS (11,20,40) or the number of PBS relative to PSII (42). Cyanobacteria grown in light that is harvested primarily by PBS show a decline in the PSII-to-PSI ratio, while those grown in light harvested primarily by PSI show the opposite response (1,26,41,44). These changes may allow cyanobacteria to balance the production of ATP and NADPH despite conditions favoring the activity of one photosystem over the other (26,43). Carbon-limited cyanobacteria show a decline in the ratio of PSII to PSI that may reflect an increase in cyclic relative to linear photosynthetic electron flow. This change could increase the production of ATP relative to NADPH and help meet the extra demand for energy incurred by cells that must actively take up inorganic carbon (36,45,51,53). Patterns of electron transport are also altered whe...

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Activities of two dissimilar thioredoxins from the cyanobacterium Anabaena sp. strain PCC 7120

Abstract: . 171: [162][163][164][165][166][167][168][169][170][171] 1989

Cited by 17 publications

References 35 publications

Thioredoxins: structure and function in plant cells

Thioredoxins: structure and function in plant cells

Purification, properties and primary structure of thioredoxin from Aspergillus nidulans

Disruption of a gene encoding a novel thioredoxin-like protein alters the cyanobacterial photosynthetic apparatus

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