 Figure1
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Introduction
Calcineurin is a serin/threonin protein phosphatases(PP2B), and is mediated by calmodulin in
Ca(II)-dependent signalling pathway.When calmodulin binded to Ca(II), it will change it's conformation
and reveal two hydrophobic patches to bind to calcineurin. Calcineurin can dephosphorylated calmodulin
and calmodulin will be actived. We have found that calcineurin is required for NaCl and LiCl tolerancel.
Calcineurin is required for K(I) vs Na(I) discrimination and converting the K(I) transport system from a
low- to a high- affinity mode at high NaCl concentration.
Structure
Calcineurin is a hetrodimer.It contains one catalytic subunit, calcineurin A encoded by cna1/cna2 gene,(Figure 1,2 about different sideview)
and one reguratory subunit, calcineurin B encoded by cnb1 gene.(Figure 3) Calcineurin B can bind to 4 free Ca(II)
and calcineurin complex will be actived.Then, calcineurin can joint two pathway.One,calcineurin A will bind to Ca(II)/calmodulin complex.
Another, calcineurin A catalytic system.Figure4 indicates the two subunits complex.
Physiological function
Calcineurin is an important phosphotase, espacially in brain. But it's functions are obscure. In different cells, it has different function.
In lymphocytes, calcineurin defectived will make T-cells fail to express IL-2 and helper T-cell misfunction.In brain, calcineurin can affect Ca(II)
channel effluxed. In renal tubule cell, it can affect Na(I)/K(I) pump.Calcineurin is nessesary to NaCl tolerance, but how does it affect is still a puzzle.
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