Elsevier

FEBS Letters

Volume 150, Issue 1, 13 December 1982, Pages 185-190
FEBS Letters

Solubilization and partial purification of protein kinase systems from brain membranes that phosphorylate calspectin: A spectrin-like calmodulin-binding protein (fodrin)

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Abstract

In brain tissue a spectrin-like calmodulin-binding protein calspectin, or fodrin, is concentrated in a synaptosome fraction, where most of the calspectin is associated with the synaptic membranes. This endogenous calspectin was phosphorylated by protein kinase system(s) associated with the membranes. Here, we report the solubilization and partial purification of the membrane-associated calspectin kinase activity. The activity was resolved on a gel filtration column into two fractions, peaks I and II having estimated Mr of 800 000 and 88 000. The activity of peak I was dependent on the presence of both Ca2+ and calmodulin. Peak II revealed a basal activity in the absence of Ca2+ and calmodulin, which was stimulated 2-fold by addition of Ca2+. Calmodulin had no effect on the peak II activity.

Keywords

Calspectin
Fodrin
Calmodulin-binding protein
Calmodulin-dependent protein kinase

Abbreviations

EGTA
ethyleneglycol bis(β-aminoethylether)-N,N,N'-tetraacetic acid
EDTA
ethylenediamine tetraacetic acid
SDS
sodium dodecyl sulfate
PMSF
phenylmethylsulfonyl fluoride
DFP
diisopropylfluorophosphate
Mr
relative molecular mass

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