Molecular Basis for Semidominance of Missense Mutations in the XANTHA-H (42-kDa) Subunit of Magnesium Chelatase
(1999) In Proceedings of the National Academy of Sciences 96(4). p.1744-1749- Abstract
- During biosynthesis of bacteriochlorophyll or chlorophyll, three protein subunits of 140, 70, and 42 kDa interact to insert Mg2+ into protoporphyrin IX. The semi-dominant Chlorina-125,-157, and -161 mutants in barley are deficient in this step and accumulate protoporphyrin IX after feeding on 5-aminolevulinate. Chlorina-125,-157, and -161 are allelic to the recessive xantha-h mutants and contain G559A, G806A, and C271T mutations, respectively. These mutations cause single amino acid substitutions in residues that are conserved in all known primary structures of the 42-kDa subunit. In vitro complementation and reconstitution of Mg-chelatase activity show that the 42-kDa subunits are defective in the semidominant Chlorina mutants. A mutated... (More)
- During biosynthesis of bacteriochlorophyll or chlorophyll, three protein subunits of 140, 70, and 42 kDa interact to insert Mg2+ into protoporphyrin IX. The semi-dominant Chlorina-125,-157, and -161 mutants in barley are deficient in this step and accumulate protoporphyrin IX after feeding on 5-aminolevulinate. Chlorina-125,-157, and -161 are allelic to the recessive xantha-h mutants and contain G559A, G806A, and C271T mutations, respectively. These mutations cause single amino acid substitutions in residues that are conserved in all known primary structures of the 42-kDa subunit. In vitro complementation and reconstitution of Mg-chelatase activity show that the 42-kDa subunits are defective in the semidominant Chlorina mutants. A mutated protein is maintained in the Chlorina plastids, unlike in the xantha-h plastids. Heterozygous Chlorina seedlings have 25-50% of the Mg-chelatase activity of wild-type seedlings. Codominant expression of active and inactive 42-kDa subunits in heterozygous Chlorina seedlings is likely to produce two types of heterodimers between the strongly interacting 42-kDa and 70-kDa subunits. Reduced Mg-chelatase activity is explained by the capacity of heterodimers consisting of mutated 42-kDa and wild-type 70-kDa protein to the 140-kDa subunit. The 42-kDa subunit is similar to chaperones that refold denatured polypeptides with respect to its ATP-to-ADP exchange activity and its ability to generate ATPase activity with the 70-kDa subunit. We hypothesize that the association of the 42-kDa subunit with the 70-kDa subunit allows them to form a specific complex with the 140-kDa subunit and that this complex inserts Mg2+ into protoporphyrin IX. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/125309
- author
- Hansson, Andreas LU ; Gamini Kannangara, C ; von Wettstein, Diter and Hansson, Mats LU
- organization
- publishing date
- 1999
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Plant Biology
- in
- Proceedings of the National Academy of Sciences
- volume
- 96
- issue
- 4
- pages
- 1744 - 1749
- publisher
- National Academy of Sciences
- external identifiers
-
- scopus:0033573997
- ISSN
- 1091-6490
- language
- English
- LU publication?
- yes
- id
- 6d18db3d-8fe7-49f5-8f1b-9e064345656f (old id 125309)
- alternative location
- http://www.pnas.org/cgi/content/abstract/96/4/1744
- date added to LUP
- 2016-04-01 12:08:14
- date last changed
- 2022-01-26 23:19:39
@article{6d18db3d-8fe7-49f5-8f1b-9e064345656f, abstract = {{During biosynthesis of bacteriochlorophyll or chlorophyll, three protein subunits of 140, 70, and 42 kDa interact to insert Mg2+ into protoporphyrin IX. The semi-dominant Chlorina-125,-157, and -161 mutants in barley are deficient in this step and accumulate protoporphyrin IX after feeding on 5-aminolevulinate. Chlorina-125,-157, and -161 are allelic to the recessive xantha-h mutants and contain G559A, G806A, and C271T mutations, respectively. These mutations cause single amino acid substitutions in residues that are conserved in all known primary structures of the 42-kDa subunit. In vitro complementation and reconstitution of Mg-chelatase activity show that the 42-kDa subunits are defective in the semidominant Chlorina mutants. A mutated protein is maintained in the Chlorina plastids, unlike in the xantha-h plastids. Heterozygous Chlorina seedlings have 25-50% of the Mg-chelatase activity of wild-type seedlings. Codominant expression of active and inactive 42-kDa subunits in heterozygous Chlorina seedlings is likely to produce two types of heterodimers between the strongly interacting 42-kDa and 70-kDa subunits. Reduced Mg-chelatase activity is explained by the capacity of heterodimers consisting of mutated 42-kDa and wild-type 70-kDa protein to the 140-kDa subunit. The 42-kDa subunit is similar to chaperones that refold denatured polypeptides with respect to its ATP-to-ADP exchange activity and its ability to generate ATPase activity with the 70-kDa subunit. We hypothesize that the association of the 42-kDa subunit with the 70-kDa subunit allows them to form a specific complex with the 140-kDa subunit and that this complex inserts Mg2+ into protoporphyrin IX.}}, author = {{Hansson, Andreas and Gamini Kannangara, C and von Wettstein, Diter and Hansson, Mats}}, issn = {{1091-6490}}, keywords = {{Plant Biology}}, language = {{eng}}, number = {{4}}, pages = {{1744--1749}}, publisher = {{National Academy of Sciences}}, series = {{Proceedings of the National Academy of Sciences}}, title = {{Molecular Basis for Semidominance of Missense Mutations in the XANTHA-H (42-kDa) Subunit of Magnesium Chelatase}}, url = {{http://www.pnas.org/cgi/content/abstract/96/4/1744}}, volume = {{96}}, year = {{1999}}, }