Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Target Concepts:
Gene/Protein
Disease
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Query: EC:3.5.4.4 (
adenosine deaminase
)
5,136
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
We describe a new member of the class of mutants in Arabidopsis exhibiting high rates of cyclic electron flow around photosystem I (CEF), a light-driven process that produces ATP but not NADPH. High cyclic electron flow 2 (
hcef2
) shows strongly increased CEF activity through the
NADPH dehydrogenase
complex (NDH), accompanied by increases in thylakoid proton motive force (
pmf
), activation of the photoprotective q
E
response, and the accumulation of H
2
O
2
. Surprisingly,
hcef2
was mapped to a non-sense mutation in the TADA1 (tRNA
adenosine deaminase
arginine) locus, coding for a plastid targeted tRNA editing enzyme required for efficient codon recognition. Comparison of protein content from representative thylakoid complexes, the cytochrome
bf
complex, and the ATP synthase, suggests that inefficient translation of
hcef2
leads to compromised complex assembly or stability leading to alterations in stoichiometries of major thylakoid complexes as well as their constituent subunits. Altered subunit stoichiometries for photosystem I, ratios and properties of cytochrome
bf
hemes, and the decay kinetics of the flash-induced thylakoid electric field suggest that these defect lead to accumulation of H
2
O
2
in
hcef2
, which we have previously shown leads to activation of NDH-related CEF. We observed similar increases in CEF, as well as increases in H
2
O
2
accumulation, in other translation defective mutants. This suggests that loss of coordination in plastid protein levels lead to imbalances in photosynthetic energy balance that leads to an increase in CEF. These results taken together with a large body of previous observations, support a general model in which processes that lead to imbalances in chloroplast energetics result in the production of H
2
O
2
, which in turn activates CEF. This activation could be from either H
2
O
2
acting as a redox signal, or by a secondary effect from H
2
O
2
inducing a deficit in ATP.
...
PMID:Defects in the Expression of Chloroplast Proteins Leads to H
2
O
2
Accumulation and Activation of Cyclic Electron Flow around Photosystem I. 2813 62
