Mechanism of activation of Saccharomyces cerevisiae calcineurin by Mn2+.

Saccharomyces cerevisiae calcineurin (CN) consists of a catalytic subunit CNA1 or CNA2 and a regulatory subunit CNB1. The kinetics of activation of yeast CN holoenzymes and their catalytic domains by Mn2+ were investigated. We report that the in vitro phosphatase reaction activated by Mn2+ typically has a pronounced initial lag ...
phase caused by slow conformational rearrangement of the holoenzyme-Mn2+. A similar lag phase was detected using just the catalytic domain of yeast CN, indicating that the slowness of Mn2+-induced conformational change of CN results from a rearrangement within the catalytic domain. The Mn2+-activation of CN was reversible. The dissociation constant of the CN heterodimer containing the CNA2 subunit in the presence of Mn2+ was 3-fold higher than that of CN containing the CNA1 subunit and that of the catalytic domains of CNA1 and CNA2, pointing to differences between the residues surrounding the Mn2+-binding sites of CNA1 and CNA2.
Mesh Terms:
Calcineurin, Catalytic Domain, Enzyme Activation, Escherichia coli, Holoenzymes, Kinetics, Magnesium, Recombinant Proteins, Saccharomyces cerevisiae, Spectrometry, Fluorescence
Biol. Chem.
Date: Nov. 01, 2009
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