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Recessiveness and dominance in barley mutants deficient in Mg-chelatase subunit D, an AAA protein involved in chlorophyll biosynthesis.
- Source :
-
The Plant cell [Plant Cell] 2006 Dec; Vol. 18 (12), pp. 3606-16. Date of Electronic Publication: 2006 Dec 08. - Publication Year :
- 2006
-
Abstract
- Mg-chelatase catalyzes the insertion of Mg2+ into protoporphyrin IX at the first committed step of the chlorophyll biosynthetic pathway. It consists of three subunits: I, D, and H. The I subunit belongs to the AAA protein superfamily (ATPases associated with various cellular activities) that is known to form hexameric ring structures in an ATP-dependant fashion. Dominant mutations in the I subunit revealed that it functions in a cooperative manner. We demonstrated that the D subunit forms ATP-independent oligomeric structures and should also be classified as an AAA protein. Furthermore, we addressed the question of cooperativity of the D subunit with barley (Hordeum vulgare) mutant analyses. The recessive behavior in vivo was explained by the absence of mutant proteins in the barley cell. Analogous mutations in Rhodobacter capsulatus and the resulting D proteins were studied in vitro. Mixtures of wild-type and mutant R. capsulatus D subunits showed a lower activity compared with wild-type subunits alone. Thus, the mutant D subunits displayed dominant behavior in vitro, revealing cooperativity between the D subunits in the oligomeric state. We propose a model where the D oligomer forms a platform for the stepwise assembly of the I subunits. The cooperative behavior suggests that the D oligomer takes an active part in the conformational dynamics between the subunits of the enzyme.
- Subjects :
- Amino Acid Sequence
Catalysis
Gene Expression Regulation, Enzymologic
Gene Expression Regulation, Plant
Lyases chemistry
Lyases genetics
Lyases metabolism
Models, Biological
Molecular Sequence Data
Mutation genetics
Phenotype
Plant Leaves enzymology
Plant Proteins chemistry
Plant Proteins genetics
Plant Proteins metabolism
Protein Folding
Protein Structure, Quaternary
Protein Subunits chemistry
Protein Subunits deficiency
Protein Subunits genetics
Protein Subunits metabolism
RNA, Messenger genetics
RNA, Messenger metabolism
Rhodobacter capsulatus ultrastructure
Seedlings enzymology
Chlorophyll biosynthesis
Genes, Dominant
Genes, Recessive
Hordeum enzymology
Hordeum genetics
Lyases deficiency
Metalloendopeptidases metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 1040-4651
- Volume :
- 18
- Issue :
- 12
- Database :
- MEDLINE
- Journal :
- The Plant cell
- Publication Type :
- Academic Journal
- Accession number :
- 17158606
- Full Text :
- https://doi.org/10.1105/tpc.106.042374