Information on EC 1.97.1.12 - photosystem I

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The expected taxonomic range for this enzyme is: Eukaryota, Bacteria

EC NUMBER
COMMENTARY hide
1.97.1.12
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RECOMMENDED NAME
GeneOntology No.
photosystem I
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REACTION
REACTION DIAGRAM
COMMENTARY hide
ORGANISM
UNIPROT
LITERATURE
reduced plastocyanin + oxidized ferredoxin + hnu = oxidized plastocyanin + reduced ferredoxin
show the reaction diagram
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PATHWAY
BRENDA Link
KEGG Link
MetaCyc Link
photosynthesis light reactions
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photosynthesis
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SYSTEMATIC NAME
IUBMB Comments
plastocyanin:ferredoxin oxidoreductase (light-dependent)
Contains chlorophyll, phylloquinones, carotenoids and [4Fe-4S] clusters. Cytochrome c6 can act as an alternative electron donor, and flavodoxin as an alternative acceptor in some species.
ORGANISM
COMMENTARY hide
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
psaA, psaB, and psaC
UniProt
Manually annotated by BRENDA team
photosystem I reaction center subunit III, plastocyanin-docking protein
SwissProt
Manually annotated by BRENDA team
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Manually annotated by BRENDA team
cv. Hitomebore
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Manually annotated by BRENDA team
Psychotria henryi
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Manually annotated by BRENDA team
GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
evolution
it is proposed that PSI evolved stepwise from a trimeric form to tetrameric oligomer en route to becoming monomeric in plants/algae
malfunction
metabolism
physiological function
additional information
SUBSTRATE
PRODUCT                       
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
reduced cytochrome b6 + oxidized ferredoxin + hv
oxidized cytochrome b6 + reduced ferredoxin
show the reaction diagram
reduced cytochrome c6 + oxidized ferredoxin + hv
oxidized cytochrome c6 + reduced ferredoxin
show the reaction diagram
reduced cytochrome c6 + oxidized flavodoxin + hv
oxidized cytochrome c6 + reduced flavodoxin
show the reaction diagram
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-
?
reduced plastocyanin + oxidized ferredoxin + hv
oxidized plastocyanin + reduced ferredoxin
show the reaction diagram
reduced plastocyanin + oxidized flavodoxin + hv
oxidized plastocyanin + reduced flavodoxin
show the reaction diagram
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?
additional information
?
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NATURAL SUBSTRATES
NATURAL PRODUCTS
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate) hide
LITERATURE
(Substrate)
COMMENTARY
(Product) hide
LITERATURE
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
reduced cytochrome b6 + oxidized ferredoxin + hv
oxidized cytochrome b6 + reduced ferredoxin
show the reaction diagram
reduced cytochrome c6 + oxidized ferredoxin + hv
oxidized cytochrome c6 + reduced ferredoxin
show the reaction diagram
reduced cytochrome c6 + oxidized flavodoxin + hv
oxidized cytochrome c6 + reduced flavodoxin
show the reaction diagram
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-
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-
?
reduced plastocyanin + oxidized ferredoxin + hv
oxidized plastocyanin + reduced ferredoxin
show the reaction diagram
reduced plastocyanin + oxidized flavodoxin + hv
oxidized plastocyanin + reduced flavodoxin
show the reaction diagram
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-
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-
?
COFACTOR
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
2,3-dichloronaphthoquinone
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in the mutant menB deletion strain
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beta-carotene
Chlorophyll
chlorophyll a
chlorophyll a'
Ferredoxin
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iron-sulfur centre
Lipid
phylloquinone
plastoquinone
[4Fe-4S] center
[4Fe-4S]-center
additional information
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METALS and IONS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
Mg2+
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variations in the luminal Mg(II) concentration may modulate the binding between plastocyanin and photosystem I subunit PsaF during the light-dark transitions, being stronger in the illuminated state. The Mg(II) ion probably is bound close to Glu43 in the lower acidic patch, and most likely in the form of a hexaquo complex embedded within the hydration shell of plastocanin, suggesting a specific binding site for Mg(II) that may regulate the binding of plastocyanin to photosystem 1 in vivo
INHIBITORS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
3-(3,4-dichlorophenyl)-1,1-dimethylurea
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DCMU
Ag(I)-substituted plastocyanin
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competitive inhibitor of the reaction with normal Cu-containg plastocyanin
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gallium ferredoxin
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superoxide
Psychotria henryi
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superoxide generated in the chloroplast stroma causes photoinhibition of photosystem I, superoxide accelerates photoinhibition of PSI
Zn(II)-substituted plastocyanin
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competitive inhibitor of the reaction with normal Cu-containg plastocyanin
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additional information
Psychotria henryi
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treatment of detached leaves with constant high light in the presence of methyl viologen (MV) or a soluble alpha-tocopherol analogue, 2,2,5,7,8-pentamethyl-6-chromanol (PMC). MV significantly depresses photochemical quantum yields in PSI and PSII when compared to PMC. Methyl viologen not only strongly downregulates electron flow from PSII to PSI (ETRII), but also intensely inhibits circular electron transport in the shade-establishing species. Activation of circular electron flow cannot prevent PSI photoinhibition in Psychotria henryi. Strong PSII photoinhibition by MV. Different mechanisms of PSI photoinhibition in higher plants, overview
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ACTIVATING COMPOUND
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
reduced DTT
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does not reduce the plastoquinone pool directly, but is dependent on ferredoxin, consistent with the involvement of a ferredoxin-dependent reaction, most likely the ferredoxin:quinone reductase (FQR)
additional information
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KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.007
reduced plastocyanin
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pH and temperature not specified in the publication
additional information
additional information
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Ki VALUE [mM]
INHIBITOR
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
IMAGE
0.03
Ag(I)-substituted plastocyanin
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pH and temperature not specified in the publication
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0.41
Zn(II)-substituted plastocyanin
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pH and temperature not specified in the publication
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pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
pH RANGE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
additional information
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cyclic electron flow around photosystem I is enhanced at low pH of 5.5. The light response curve of PS I is significantly affected by acidification of the thylakoid membranes
TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
SOURCE
Psychotria henryi
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Manually annotated by BRENDA team
LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY hide
GeneOntology No.
LITERATURE
SOURCE
PDB
SCOP
CATH
UNIPROT
ORGANISM
Arabidopsis thaliana;
Cyanidioschyzon merolae (strain 10D);
Pisum sativum;
Synechocystis sp. (strain PCC 6803 / Kazusa);
Thermosynechococcus elongatus (strain BP-1);
MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
106800
tetrameric enzyme form, blue native PAGE
SUBUNITS
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
?
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21000-22000 Da, photosystem 1 subunit PsaF that is involved in the docking of the electron-donor proteins plastocyanin and cytochrome c6, SDS-PAGE
dimer
in strain TS-821 PSI forms tetrameric, dimeric, and monomeric species, a tetrameric PSI has two PSI dimers associated together with interdimer gaps, while the PSI dimer is composed of two tightly tethered PSI monomers, subunit organization, structure comparisons, overview
heterotetramer
two-dimensional maps obtained by single particle electron microscopy clearly show that the tetramer lacks four-fold symmetry and is actually composed of a dimer of dimers with C2 symmetry, cryo-electron microscopy is used for 3D reconstruction of the PSI tetramer complex and a 3D model at 11.5 A resolution is obtained. A 2D map within the membrane plane of about 6.1 A is used for modeling, structure model comparison with the PSI structure of Thermosynechococcus elongatus at 2.5 A, PDB ID 1JB0, overview. The PsaL subunit of strain TS-821 is modeled using PsaL subunit of Pisum sativum as a template, PDB ID 4Y28L. The modeled PsaL subunit of TS-821 is used to substitute the existing PsaL subunit in crystal structure of Thermosynechococcus elongatus and most of the subunits from the crystal structure of Thermosynechococcus elongatus are fitted separately into the 3D volumemap of TS-821. Comparison of trimeric interface of Thermosynechococcus elongatus with interface type 1 of TS-821
monomer
tetramer
in strain TS-821 PSI forms tetrameric, dimeric, and monomeric species, a tetrameric PSI has two PSI dimers associated together with interdimer gaps, while the PSI dimer is composed of two tightly tethered PSI monomers, subunit organization, structure comparisons, overview
trimer
additional information
Crystallization/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
3.3 A crystal structure of the entire PSI super-complex, sitting drop variant of the vapor-diffusion technique at 4°C
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purified plant photosystem I supercomplex including light-harvesting complex I, sitting drop vapour diffusion technique, mixing of 0.006-0.008 ml of PSI protein solution with an equal volume of reservoir solution containing 50 mM di-potassium phosphate, 50 mM Tris, pH 8, 12-17% PEG 400, 1% glycerol, 2 mM L-glutathione, and 0.03% octyl glucose neopentyl glycol, and equilibration against 0.5 ml of reservoir solution, 4°C, 1 month, X-ray diffraction structure determination and analysis at 2.6 A resolution, single-wavelength anomalous diffraction phasing of PSI-LHCI
sitting-drop variant of the vapour-diffusion technique at 4°C, crystals diffract to 4 A resolution using synchrotron radiation and belong to the monoclinic crystal system, space group P21, with unit-cell parameters a = 181.90, b = 190.24, c = 219.66 A, beta = 90.484
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single crystals from a complex of photosystem I with ferredoxin are grown using PEG 400 and CaCl2 as precipitation agents. The crystals diffract X-rays to a resolution of 7–8 A. The space group iss determined to be orthorhombic with the unit cell dimensions a = 194 A, b = 208 A, and c = 354 A. The crystals contain photosystem I and ferredoxin in a 1:1 ratio. Electron paramagnetic resonance (EPR) measurements on these crystals are reported, where EPR signals of the three [4Fe-4S] clusters FA, FB, FX, and the [2Fe-2S] cluster of ferredoxin are detected
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highly ordered two-dimensional crystals of photosystem I reaction center complex
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isolation and reconstitution of the functional PSI complexes into 2D arrays. The solubilized and crystallized PSI has essentially the same protein composition, as shown by SDS/polyacrylamide gels
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TEMPERATURE STABILITY
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
20 - 100
analysis of thermostability of oligomeric PSI complexes. The thermal profile of the spectral shift of alpha-helices bands confirms the same two temperature intervals for PSI monomers and only one interval for trimers. Spectra at 20-100°C show distinct changes in the Amide I region of PSI complexes as a function of the rising temperature. Absorbance at the Amide I maximum of PSI monomers, gradually drops in two temperature intervals, i.e. 60-75°C and 80-90°C. In contrast, absorbance at the Amide I maximum of PSI trimers drops only in one temperature interval 80-95°C. Spectral changes of PSI trimers and monomers heated up to 100°C are irreversible due to protein denaturation and non-specific aggregation of complexes leading to new absorption bands. Thermal denaturation profiles, detailed overview, The enzyme shows denaturation at the monomer-monomer-interface at over 60°C, and denaturation/aggregation at the trimer-lipid interface at over 80°C. Oligomerization is one strategy to increase thermostability of PSI complexes
additional information
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a group of short amphiphilic peptides improve the thermal stability of the multi-domain protein complex photosystem-I in aqueous solution. Ac-I5K2-CONH2 shows the best stabilizing effect by enhancing the melting temperature of PS-I from 48°C to 53°C at concentration of 0.65 mM and extending the half life of isolated PS-I significantly
GENERAL STABILITY
ORGANISM
UNIPROT
LITERATURE
a group of short amphiphilic peptides improve the thermal stability of the multi-domain protein complex photosystem-I in aqueous solution. Ac-I5K2-CONH2 shows the best stabilizing effect by enhancing the melting temperature of PS-I from 48°C to 53°C at concentration of 0.65 mM and extending the half life of isolated PS-I significantly
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acetyl-VVVVVVD stabilizes the photosystem I complex to a lesser extent than acetyl-AAAAAAK
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dodecyl-beta-D-maltoside partially stabilizes
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in the presence of acetyl-AAAAAAK, the PS-I complex is stable in a dried form at room temperature for at least 3 weeks
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octyl-beta-D-glucoside partially stabilizes
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Purification/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
from thyloakoid membranes, by detergent solubilization
native enzyme complex from detergent-treated thylakoid membranes by two steps of anion exchange chromatography with elution through tetraethylammonium chloride followed by precipitation with PEG 6000 and PEG 1500, respectively
PsaE protein is purified to homogeneity by affinity chromatography. Subunit PsaE (a peripheral subunit of the PSI complex)is involved in the docking of ferredoxin/flavodoxin to the PSI complex and also participates in the cyclic electron transfer around phosposystem I
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purification of the luminal domain of spinach photosystem 1 subunit PsaF
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rapid, high-yield purification of PS1
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recombinant His6-tagged enzyme from thylakoid membranes by nickel affinity chromatography and ultrafiltration
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Cloned/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
cloning of the luminal domain of spinach photosystem 1 subunit PsaF, expressed in Escherichia coli BL21 (DE3) using a pET32 Xa/LIC thioredoxin fusion system
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gene psaL encoding PsaL protein that contains a short insert between the second and third predicted transmembrane helices of the enzyme, phylogenetic analysis
PSI genes quantitative real-time PCR expression analysis
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the psaE gene is cloned and overexpressed in Escherichia coli. PsaE (a peripheral subunit of the PSI complex) is involved in the docking of ferredoxin/flavodoxin to the PSI complex and also participates in the cyclic electron transfer around phosposystem I
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EXPRESSION
ORGANISM
UNIPROT
LITERATURE
protein WHY1 affects the expression of PSI-LHCI encoding genes. A large number of genes encoding the PSI core complex are upregulated in both the nucleus and plastids of overexpressing WHY1 plants (oepnWHY1), whereas the transcription level of LHCA1-6 is steady
ENGINEERING
ORGANISM
UNIPROT
COMMENTARY hide
LITERATURE
D612H/E613H
mutation in subunit PsaB of photosystem I. Photosystem I harboring the has a high affinity toward binding of the electron donors and possesses an altered pH dependence of electron transfer with plastocyanin and cytochrome c6. The mutant strain exhibits a strong light sensitive growth phenotype, indicating that decelerated turnover between plastocyanin/cytochrome c6 and photosystem I with respect to electron transfer is deleterious to the cells
F689N
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site-directed mutagenesis of subunit PsaA, the mutation causes in an about 100fold decrease in the observed rate of cofactor phylloquinone PhQA- oxidation, resulting in a lifetime that exceeds that of the terminal electron donor, P700+. This situation allows a second photochemical charge separation event to be initiated before PhQA- has decayed, thereby mimicking in PSI a situation that occurs in type II reaction centers. Simulation of the pump-pump kinetics in PsaA-F689N, overview
N591L
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site-directed mutagenesis of psaB, the mutant shows structural differences and altered activity compared to the wild-type enzyme, detailed overview
N604L
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site-directed mutagenesis of psaA, the mutant shows structural differences and altered activity compared to the wild-type enzyme, detailed overview
F689N
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site-directed mutagenesis of subunit PsaA, the mutation causes in an about 100fold decrease in the observed rate of cofactor phylloquinone PhQA- oxidation, resulting in a lifetime that exceeds that of the terminal electron donor, P700+. This situation allows a second photochemical charge separation event to be initiated before PhQA- has decayed, thereby mimicking in PSI a situation that occurs in type II reaction centers. Simulation of the pump-pump kinetics in PsaA-F689N, overview
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F647C
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mutant strain cannot grow under photoautotrophic conditions because of low photosystem I activity, possibly due to low levels of proteins
F649C/G650I
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mutant strain cannot grow under photoautotrophic conditions because of low photosystem I activity, possibly due to low levels of proteins
H651C/L652M
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mutant strain cannot grow under photoautotrophic conditions because of low photosystem I activity, possibly due to low levels of proteins
S641C/V642I
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mutation in subunit PsaB. Mutant strain grows photoautotrophically and shows no obvious reduction in the photosystem I activity. Kinetics of P700 re-reduction by plastocyanin remains unaltered
W643C/A644I
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mutation in subunit PsaB. Mutant strain grows photoautotrophically and shows no obvious reduction in the photosystem I activity. Kinetics of P700 re-reduction by plastocyanin remains unaltered
W645C
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mutation in subunit PsaB. Mutant strain grows photoautotrophically and shows no obvious reduction in the photosystem I activity. Kinetics of P700 re-reduction by plastocyanin remains unaltered
N591L
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site-directed mutagenesis of psaB, the mutant shows structural differences and altered activity compared to the wild-type enzyme, detailed overview
N604L
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site-directed mutagenesis of psaA, the mutant shows structural differences and altered activity compared to the wild-type enzyme, detailed overview
additional information
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