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ATPase activity of magnesium chelatase subunit I is required to maintain subunit D in vivo

Lake, Vanessa; Olsson, Ulf LU ; Willows, RD and Hansson, Mats LU (2004) In European Journal of Biochemistry 271(11). p.2182-2188
Abstract
During biosynthesis of chlorophyll, Mg2+ is inserted into protoporphyrin IX by magnesium chelatase. This enzyme consists of three different subunits of approximate to 40, 70 and 140 kDa. Seven barley mutants deficient in the 40 kDa magnesium chelatase subunit were analysed and it was found that this subunit is essential for the maintenance of the 70 kDa subunit, but not the 140 kDa subunit. The 40 kDa subunit has been shown to belong to the family of proteins called 'ATPases associated with various cellular activities', known to form ring-shaped oligomeric complexes working as molecular chaperones. Three of the seven barley mutants are semidominant mis-sense mutations leading to changes of conserved amino acid residues in the 40 kDa... (More)
During biosynthesis of chlorophyll, Mg2+ is inserted into protoporphyrin IX by magnesium chelatase. This enzyme consists of three different subunits of approximate to 40, 70 and 140 kDa. Seven barley mutants deficient in the 40 kDa magnesium chelatase subunit were analysed and it was found that this subunit is essential for the maintenance of the 70 kDa subunit, but not the 140 kDa subunit. The 40 kDa subunit has been shown to belong to the family of proteins called 'ATPases associated with various cellular activities', known to form ring-shaped oligomeric complexes working as molecular chaperones. Three of the seven barley mutants are semidominant mis-sense mutations leading to changes of conserved amino acid residues in the 40 kDa protein. Using the Rhodobacter capsulatus 40 and 70 kDa magnesium chelatase subunits we have analysed the effect of these mutations. Although having no ATPase activity, the deficient 40 kDa subunit could still associate with the 70 kDa protein. The binding was dependent on Mg2+ and ATP or ADP. Our study demonstrates that the 40 kDa subunit functions as a chaperon that is essential for the survival of the 70 kDa subunit in vivo. We conclude that the ATPase activity of the 40 kDa subunit is essential for this function and that binding between the two subunits is not sufficient to maintain the 70 kDa subunit in the cell. The ATPase deficient 40 kDa proteins fail to participate in chelation in a step after the association of the 40 and 70 kDa subunits. This step presumably involves a conformational change of the complex in response to ATP hydrolysis. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
AAA, barley, chlorophyll, magnesium chelatase, Rhodobacter capsulatus
in
European Journal of Biochemistry
volume
271
issue
11
pages
2182 - 2188
publisher
Wiley-Blackwell
external identifiers
  • wos:000221533600017
  • pmid:15153108
  • scopus:2942574369
ISSN
0014-2956
DOI
10.1111/j.1432-1033.2004.04143.x
language
English
LU publication?
yes
id
9adb9228-327d-4897-80c5-5e3c43e03fe1 (old id 126449)
date added to LUP
2007-07-05 16:55:49
date last changed
2017-02-26 04:17:01
@article{9adb9228-327d-4897-80c5-5e3c43e03fe1,
  abstract     = {During biosynthesis of chlorophyll, Mg2+ is inserted into protoporphyrin IX by magnesium chelatase. This enzyme consists of three different subunits of approximate to 40, 70 and 140 kDa. Seven barley mutants deficient in the 40 kDa magnesium chelatase subunit were analysed and it was found that this subunit is essential for the maintenance of the 70 kDa subunit, but not the 140 kDa subunit. The 40 kDa subunit has been shown to belong to the family of proteins called 'ATPases associated with various cellular activities', known to form ring-shaped oligomeric complexes working as molecular chaperones. Three of the seven barley mutants are semidominant mis-sense mutations leading to changes of conserved amino acid residues in the 40 kDa protein. Using the Rhodobacter capsulatus 40 and 70 kDa magnesium chelatase subunits we have analysed the effect of these mutations. Although having no ATPase activity, the deficient 40 kDa subunit could still associate with the 70 kDa protein. The binding was dependent on Mg2+ and ATP or ADP. Our study demonstrates that the 40 kDa subunit functions as a chaperon that is essential for the survival of the 70 kDa subunit in vivo. We conclude that the ATPase activity of the 40 kDa subunit is essential for this function and that binding between the two subunits is not sufficient to maintain the 70 kDa subunit in the cell. The ATPase deficient 40 kDa proteins fail to participate in chelation in a step after the association of the 40 and 70 kDa subunits. This step presumably involves a conformational change of the complex in response to ATP hydrolysis.},
  author       = {Lake, Vanessa and Olsson, Ulf and Willows, RD and Hansson, Mats},
  issn         = {0014-2956},
  keyword      = {AAA,barley,chlorophyll,magnesium chelatase,Rhodobacter capsulatus},
  language     = {eng},
  number       = {11},
  pages        = {2182--2188},
  publisher    = {Wiley-Blackwell},
  series       = {European Journal of Biochemistry},
  title        = {ATPase activity of magnesium chelatase subunit I is required to maintain subunit D in vivo},
  url          = {http://dx.doi.org/10.1111/j.1432-1033.2004.04143.x},
  volume       = {271},
  year         = {2004},
}