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ATPases and phosphate exchange activities in magnesium chelatase subunits of Rhodobacter sphaeroides

Hansson, Mats LU and Kannangara, C. G. (1997) In Proceedings of the National Academy of Sciences 94(24). p.13351-13356
Abstract
Three separate proteins, BchD, BchH, and BchI, together with ATP, insert magnesium into protoporphyrin IX. An analysis of ATP utilization by the subunits revealed the following: BchH catalyzed ATP hydrolysis at the rate of 0.9 nmol per min per mg of protein. BchI and BchD, tested individually, had no ATPase activity but, when combined, hydrolyzed ATP at the rate of 117.9 nmol/min per mg of protein. Magnesium ions were required for the ATPase activities of both BchH and BchI+D, and these activities were inhibited 50% by 2 mM o-phenanthroline. BchI additionally catalyzed a phosphate exchange reaction from ATP and ADP. We conclude that ATP hydrolysis by BchI+D is required for an activation step in the magnesium chelatase reaction, whereas... (More)
Three separate proteins, BchD, BchH, and BchI, together with ATP, insert magnesium into protoporphyrin IX. An analysis of ATP utilization by the subunits revealed the following: BchH catalyzed ATP hydrolysis at the rate of 0.9 nmol per min per mg of protein. BchI and BchD, tested individually, had no ATPase activity but, when combined, hydrolyzed ATP at the rate of 117.9 nmol/min per mg of protein. Magnesium ions were required for the ATPase activities of both BchH and BchI+D, and these activities were inhibited 50% by 2 mM o-phenanthroline. BchI additionally catalyzed a phosphate exchange reaction from ATP and ADP. We conclude that ATP hydrolysis by BchI+D is required for an activation step in the magnesium chelatase reaction, whereas ATPase activity of BchH and the phosphate exchange activity of BchI participate in subsequent reactions leading to the insertion of Mg2+ into protoporphyrin IX. (Less)
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published
subject
keywords
Adenosine Diphosphate/metabolism, Adenosine Triphosphatases/antagonists & inhibitors/*metabolism, Enzyme Activation, Enzyme Inhibitors/pharmacology, Lyases/antagonists & inhibitors/chemistry/*metabolism, Phenanthrolines/pharmacology, Phosphates/*metabolism, Protoporphyrins/chemistry, Rhodobacter sphaeroides/*enzymology, Sodium Fluoride/pharmacology
in
Proceedings of the National Academy of Sciences
volume
94
issue
24
pages
13351 - 13356
publisher
National Acad Sciences
external identifiers
  • scopus:0030695453
ISSN
1091-6490
DOI
10.1073/pnas.94.24.13351
language
English
LU publication?
no
id
5527c29f-0d83-402d-af0d-ffb3085be4a0 (old id 8001545)
alternative location
http://www.ncbi.nlm.nih.gov/pubmed/9371849
date added to LUP
2015-09-30 14:39:30
date last changed
2017-01-01 05:11:29
@article{5527c29f-0d83-402d-af0d-ffb3085be4a0,
  abstract     = {Three separate proteins, BchD, BchH, and BchI, together with ATP, insert magnesium into protoporphyrin IX. An analysis of ATP utilization by the subunits revealed the following: BchH catalyzed ATP hydrolysis at the rate of 0.9 nmol per min per mg of protein. BchI and BchD, tested individually, had no ATPase activity but, when combined, hydrolyzed ATP at the rate of 117.9 nmol/min per mg of protein. Magnesium ions were required for the ATPase activities of both BchH and BchI+D, and these activities were inhibited 50% by 2 mM o-phenanthroline. BchI additionally catalyzed a phosphate exchange reaction from ATP and ADP. We conclude that ATP hydrolysis by BchI+D is required for an activation step in the magnesium chelatase reaction, whereas ATPase activity of BchH and the phosphate exchange activity of BchI participate in subsequent reactions leading to the insertion of Mg2+ into protoporphyrin IX.},
  author       = {Hansson, Mats and Kannangara, C. G.},
  issn         = {1091-6490},
  keyword      = {Adenosine Diphosphate/metabolism,Adenosine Triphosphatases/antagonists & inhibitors/*metabolism,Enzyme Activation,Enzyme Inhibitors/pharmacology,Lyases/antagonists & inhibitors/chemistry/*metabolism,Phenanthrolines/pharmacology,Phosphates/*metabolism,Protoporphyrins/chemistry,Rhodobacter sphaeroides/*enzymology,Sodium Fluoride/pharmacology},
  language     = {eng},
  number       = {24},
  pages        = {13351--13356},
  publisher    = {National Acad Sciences},
  series       = {Proceedings of the National Academy of Sciences},
  title        = {ATPases and phosphate exchange activities in magnesium chelatase subunits of Rhodobacter sphaeroides},
  url          = {http://dx.doi.org/10.1073/pnas.94.24.13351},
  volume       = {94},
  year         = {1997},
}