Calcineurin B (CLNB)
entry list
alignment
Calcineurin B (CLNB) is the regulatory subunit and calcineurin A is
the catalytic subunit of a protein phosphatase. Calmodulin also binds
to calcineurin A; both CLNB and CAM in their calcium forms are required
for catalytic activity. The crystal structure of Ca4-CLNB, complexed
with an _-helical fragment (350-370) of calcineurin A and with the drug
complex, FKBP12-FK506, [17, 18] shows both lobe 1,2 and lobe 3,4
embracing the fragment in their grooves homologous to those of CAM and
TNC. In CLNB the two lobes bind to the same side of the target and are
displaced about 22 _ along it. In contrast the two lobes of CAM enfold
the target peptide from myosin light chain kinase on opposite sides and
are related by an approximate two fold rotation axis. The seven
subfamilies (CLNB, P22, VIS CALS, DREM, CMPK, and SOS3) are reasonably
congruent (figure 6).