ATPase activity associated with the magnesium chelatase H-subunit of the chlorophyll biosynthetic pathway is an artefact
(2006) In Biochemical Journal 400. p.477-484- Abstract
- Magnesium chelatase inserts Mg2+ into protoporphyrin IX and is the first unique enzyme of the chlorophyll biosynthetic pathway. It is a heterotrimeric enzyme, composed of I- (40 kDa), D- (70 kDa) and H- (140 kDa) subunits. The I- and D-proteins belong to the family of AAA(+) (ATPases associated with various cellular activities), but only I-subunit hydrolyses ATP to ADP. The D-subunits provide a platform for the assembly of the I-subunits, which results in a two-tiered hexameric ring complex. However, the D-subunits are unstable in the chloroplast unless ATPase active I-subunits are present. The H-subunit binds protoporphyrin and is suggested to be the catalytic subunit. Previous studies have indicated that the H-subunit also has ATPase... (More)
- Magnesium chelatase inserts Mg2+ into protoporphyrin IX and is the first unique enzyme of the chlorophyll biosynthetic pathway. It is a heterotrimeric enzyme, composed of I- (40 kDa), D- (70 kDa) and H- (140 kDa) subunits. The I- and D-proteins belong to the family of AAA(+) (ATPases associated with various cellular activities), but only I-subunit hydrolyses ATP to ADP. The D-subunits provide a platform for the assembly of the I-subunits, which results in a two-tiered hexameric ring complex. However, the D-subunits are unstable in the chloroplast unless ATPase active I-subunits are present. The H-subunit binds protoporphyrin and is suggested to be the catalytic subunit. Previous studies have indicated that the H-subunit also has ATPase activity, which is in accordance with an earlier suggested two-stage mechanism of the reaction. In the present study, we demonstrate that gel filtration chromatography of affinity-purified Rhodobacter capsulatus H-subunit produced in Escherichia coli generates a high- and a low-molecular-mass fraction. Both fractions were dominated by the H-subunit, but the ATPase activity was only found in the high-molecular-mass fraction and magnesium chelatase activity was only associated with the low-molecular-mass fraction. We demonstrated that light converted monomeric low-molecular-mass H-subunit into high-molecular-mass aggregates. We conclude that ATP utilization by magnesium chelatase is solely connected to the I-subunit and suggest that a contaminating E. coli protein, which binds to aggregates of the H-subunit, caused the previously reported ATPase activity of the H-subunit. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/681979
- author
- Sirijovski, Nick LU ; Olsson, Ulf LU ; Lundqvist, Joakim LU ; Al-Karadaghi, Salam LU ; Willows, Robert D. and Hansson, Mats LU
- organization
- publishing date
- 2006
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Rhodobacter, capsulatus, protoporphyrin IX, magnesium chelatase, chlorophyll, ATPases associated with various cellular activities (AAA(+)), bchH
- in
- Biochemical Journal
- volume
- 400
- pages
- 477 - 484
- publisher
- Portland Press
- external identifiers
-
- wos:000242983200011
- scopus:33845722688
- ISSN
- 0264-6021
- DOI
- 10.1042/BJ20061103
- language
- English
- LU publication?
- yes
- id
- 275bda58-3383-4d0f-ac98-b57074a3a9eb (old id 681979)
- date added to LUP
- 2016-04-01 15:59:21
- date last changed
- 2022-01-28 08:33:19
@article{275bda58-3383-4d0f-ac98-b57074a3a9eb, abstract = {{Magnesium chelatase inserts Mg2+ into protoporphyrin IX and is the first unique enzyme of the chlorophyll biosynthetic pathway. It is a heterotrimeric enzyme, composed of I- (40 kDa), D- (70 kDa) and H- (140 kDa) subunits. The I- and D-proteins belong to the family of AAA(+) (ATPases associated with various cellular activities), but only I-subunit hydrolyses ATP to ADP. The D-subunits provide a platform for the assembly of the I-subunits, which results in a two-tiered hexameric ring complex. However, the D-subunits are unstable in the chloroplast unless ATPase active I-subunits are present. The H-subunit binds protoporphyrin and is suggested to be the catalytic subunit. Previous studies have indicated that the H-subunit also has ATPase activity, which is in accordance with an earlier suggested two-stage mechanism of the reaction. In the present study, we demonstrate that gel filtration chromatography of affinity-purified Rhodobacter capsulatus H-subunit produced in Escherichia coli generates a high- and a low-molecular-mass fraction. Both fractions were dominated by the H-subunit, but the ATPase activity was only found in the high-molecular-mass fraction and magnesium chelatase activity was only associated with the low-molecular-mass fraction. We demonstrated that light converted monomeric low-molecular-mass H-subunit into high-molecular-mass aggregates. We conclude that ATP utilization by magnesium chelatase is solely connected to the I-subunit and suggest that a contaminating E. coli protein, which binds to aggregates of the H-subunit, caused the previously reported ATPase activity of the H-subunit.}}, author = {{Sirijovski, Nick and Olsson, Ulf and Lundqvist, Joakim and Al-Karadaghi, Salam and Willows, Robert D. and Hansson, Mats}}, issn = {{0264-6021}}, keywords = {{Rhodobacter; capsulatus; protoporphyrin IX; magnesium chelatase; chlorophyll; ATPases associated with various cellular activities (AAA(+)); bchH}}, language = {{eng}}, pages = {{477--484}}, publisher = {{Portland Press}}, series = {{Biochemical Journal}}, title = {{ATPase activity associated with the magnesium chelatase H-subunit of the chlorophyll biosynthetic pathway is an artefact}}, url = {{http://dx.doi.org/10.1042/BJ20061103}}, doi = {{10.1042/BJ20061103}}, volume = {{400}}, year = {{2006}}, }