Catalytic turnover triggers exchange of subunits of the magnesium chelatase AAA+ motor unit
(2013) In Journal of Biological Chemistry 288(33). p.24012-24019- Abstract
- The ATP-dependent insertion of Mg(2+) into protoporphyrin IX is the first committed step in the chlorophyll biosynthetic pathway. The reaction is catalyzed by magnesium chelatase, which consists of three gene products: BchI, BchD, and BchH. The BchI and BchD subunits belong to the family of AAA+ proteins (ATPases associated with various cellular activities) and form a two-ring complex with six BchI subunits in one layer and six BchD subunits in the other layer. This BchID complex is a two-layered trimer of dimers with the ATP binding site located at the interface between two neighboring BchI subunits. ATP hydrolysis by the BchID motor unit fuels the insertion of Mg(2+) into the porphyrin by the BchH subunit. In the present study, we... (More)
- The ATP-dependent insertion of Mg(2+) into protoporphyrin IX is the first committed step in the chlorophyll biosynthetic pathway. The reaction is catalyzed by magnesium chelatase, which consists of three gene products: BchI, BchD, and BchH. The BchI and BchD subunits belong to the family of AAA+ proteins (ATPases associated with various cellular activities) and form a two-ring complex with six BchI subunits in one layer and six BchD subunits in the other layer. This BchID complex is a two-layered trimer of dimers with the ATP binding site located at the interface between two neighboring BchI subunits. ATP hydrolysis by the BchID motor unit fuels the insertion of Mg(2+) into the porphyrin by the BchH subunit. In the present study, we explored mutations that were originally identified in semidominant barley (Hordeum vulgare L.) mutants. The resulting recombinant BchI proteins have marginal ATPase activity and cannot contribute to magnesium chelatase activity although they apparently form structurally correct complexes with BchD. Mixing experiments with modified and wild-type BchI in various combinations showed that an exchange of BchI subunits in magnesium chelatase occurs during the catalytic cycle, which indicates that dissociation of the complex may be part of the reaction mechanism related to product release. Mixing experiments also showed that more than three functional interfaces in the BchI ring structure are required for magnesium chelatase activity. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/8001682
- author
- Lundqvist, J. ; Braumann, I. ; Kurowska, M. ; Muller, A. H. and Hansson, Mats LU
- publishing date
- 2013
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Adenosine Triphosphatases/chemistry/metabolism, Adenosine Triphosphate/metabolism, *Biocatalysis, Chlorophyll/metabolism, Hordeum/*enzymology, Lyases/chemistry/*metabolism/ultrastructure, Molecular Motor Proteins/*metabolism, Mutation/genetics, Protein Multimerization, Protein Subunits/chemistry/*metabolism, Spectrophotometry, Aaa, ATPases, Biosynthesis, Chelatase, Chlorophyll Biosynthesis, Magnesium, Magnesium Chelatase, Plant Biochemistry, Porphyrin, Protoporphyrin
- in
- Journal of Biological Chemistry
- volume
- 288
- issue
- 33
- pages
- 24012 - 24019
- publisher
- American Society for Biochemistry and Molecular Biology
- external identifiers
-
- scopus:84882386220
- pmid:23836887
- ISSN
- 1083-351X
- DOI
- 10.1074/jbc.M113.480012
- language
- English
- LU publication?
- no
- additional info
- 33
- id
- 5b6f0219-127d-41f6-813e-34bb6ab5af97 (old id 8001682)
- alternative location
- http://www.ncbi.nlm.nih.gov/pubmed/23836887
- date added to LUP
- 2016-04-04 08:25:54
- date last changed
- 2022-02-28 04:50:28
@article{5b6f0219-127d-41f6-813e-34bb6ab5af97, abstract = {{The ATP-dependent insertion of Mg(2+) into protoporphyrin IX is the first committed step in the chlorophyll biosynthetic pathway. The reaction is catalyzed by magnesium chelatase, which consists of three gene products: BchI, BchD, and BchH. The BchI and BchD subunits belong to the family of AAA+ proteins (ATPases associated with various cellular activities) and form a two-ring complex with six BchI subunits in one layer and six BchD subunits in the other layer. This BchID complex is a two-layered trimer of dimers with the ATP binding site located at the interface between two neighboring BchI subunits. ATP hydrolysis by the BchID motor unit fuels the insertion of Mg(2+) into the porphyrin by the BchH subunit. In the present study, we explored mutations that were originally identified in semidominant barley (Hordeum vulgare L.) mutants. The resulting recombinant BchI proteins have marginal ATPase activity and cannot contribute to magnesium chelatase activity although they apparently form structurally correct complexes with BchD. Mixing experiments with modified and wild-type BchI in various combinations showed that an exchange of BchI subunits in magnesium chelatase occurs during the catalytic cycle, which indicates that dissociation of the complex may be part of the reaction mechanism related to product release. Mixing experiments also showed that more than three functional interfaces in the BchI ring structure are required for magnesium chelatase activity.}}, author = {{Lundqvist, J. and Braumann, I. and Kurowska, M. and Muller, A. H. and Hansson, Mats}}, issn = {{1083-351X}}, keywords = {{Adenosine Triphosphatases/chemistry/metabolism; Adenosine Triphosphate/metabolism; *Biocatalysis; Chlorophyll/metabolism; Hordeum/*enzymology; Lyases/chemistry/*metabolism/ultrastructure; Molecular Motor Proteins/*metabolism; Mutation/genetics; Protein Multimerization; Protein Subunits/chemistry/*metabolism; Spectrophotometry; Aaa; ATPases; Biosynthesis; Chelatase; Chlorophyll Biosynthesis; Magnesium; Magnesium Chelatase; Plant Biochemistry; Porphyrin; Protoporphyrin}}, language = {{eng}}, number = {{33}}, pages = {{24012--24019}}, publisher = {{American Society for Biochemistry and Molecular Biology}}, series = {{Journal of Biological Chemistry}}, title = {{Catalytic turnover triggers exchange of subunits of the magnesium chelatase AAA+ motor unit}}, url = {{http://dx.doi.org/10.1074/jbc.M113.480012}}, doi = {{10.1074/jbc.M113.480012}}, volume = {{288}}, year = {{2013}}, }