Effect of Free and ATP-Bound Magnesium and Manganese Ions on the ATPase Activity of Chaperonin GroEL14

Sophia Diamant, Abdussalam Azem, Celeste Weiss, Pierre Goloubinoff*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Hydrolysis of ATP by the GroEL14 chaperonin oligomer is activated and modulated by Mg2+ or Mn2+ ions. Mg-ATP and Mn-ATP can serve as substrates of the reaction and bind in a positively cooperative manner to the same catalytic sites on GroEL14, with similar binding constants in the micromolar range. In addition, millimolar amounts of Mg2+ and Mn2+ ions can further activate the GroEL14-ATPase while interacting with low-affinity noncatalytic sites on the chaperonin. The extent of ATPase activation by Mn2+ is half of that by Mg2+ ions. When both Mg2+ and Mn2+ ions are present in the same reaction, Mn2+ behaves as a noncompetitive partial inhibitor of the Mg-dependent ATPase. This inhibition requires the presence of ADP in the catalytic site. The binding affinity of Mn-ADP to the site is significantly higher than that of Mg-ADP. A slower release of Mn-ADP from the catalytic site thus changes the rate-determining step of the GroEL14-ATPase cycle. In the cell, the concentrations of Mg2+ and Mn2+ ions are such that both divalent ions may modulate chaperonin activity.

Original languageEnglish
Pages (from-to)273-277
Number of pages5
JournalBiochemistry
Volume34
Issue number1
DOIs
StatePublished - 1995
Externally publishedYes

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