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Membrane-bound diiron carboxylate proteins
Deborah A Berthold1, Pål Stenmark
1Department of Biochemistry and Biophysics, Arrhenius Laboratory for Natural Sciences, Stockholm University, Svante Arrhenius väg 12, SE-106 91 Stockholm, Sweden. berthold@dbb.su.se
Annual Review of Plant Biology
|September 25, 2003
Summary
Four newly identified membrane-bound diiron carboxylate proteins are crucial for respiration and photosynthesis. These proteins, including alternative oxidase (AOX) and plastid terminal oxidase (PTOX), bind to membrane leaflets and utilize quinol substrates.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- Four proteins identified as diiron carboxylate proteins based on conserved iron-binding motif.
- These proteins differ from known ones as they are membrane-bound, but not transmembrane.
Purpose of the Study:
- To characterize the structure and function of four newly identified diiron carboxylate proteins.
- To elucidate their roles in cellular respiration and photosynthesis.
Main Methods:
- Homology modeling to predict protein structure.
- Biochemical studies to determine membrane binding and substrate utilization.
- Analysis of conserved amino acid residues for iron-binding motif identification.
Main Results:
- Identified four monotopically membrane-bound diiron carboxylate proteins: AOX, PTOX, DMQ hydroxylase, and MME hydroxylase.
- Three enzymes use quinol substrates; two oxidize (AOX, PTOX), one hydroxylates (DMQ hydroxylase).
- MME hydroxylase is vital for chlorophyll synthesis; AOX and DMQ hydroxylase are involved in respiration; PTOX and MME hydroxylase in photosynthesis.
Conclusions:
- The identified proteins are interfacially bound with a diiron carboxylate active site.
- These enzymes play significant roles in both respiration and photosynthesis pathways.
- Understanding their unique membrane-binding mode offers insights into their function.