Activation of protein kinase C by purified bovine brain 14-3-3: comparison with tyrosine hydroxylase activation.

In the course of the purification of 14-3-3 protein (14-3-3) we found that 14-3-3 isolated from bovine forebrain activates protein kinase C rather than the previously reported protein kinase C inhibitory activity (KCIP). We have characterized the 14-3-3 activation of The physical properties of purified activator are the same as those previously reported for 14-3-3 and KCIP; i.e., (1) it is composed of subunits of molecular weight 32,000, 30,000, and 29,000; (2) it is homogeneous with respect to molecular weight, as judged by native gradient-gel electrophoresis, with a molecular weight of 53,000; and (3) it is composed of at least six isoforms when analyzed by reverse-phase HPLC. The concentration dependence of duanyu1531 activation by 14-3-3 is in the same range as that shown previously for KCIP inhibition of and as that required for 14-3-3 activation of tyrosine hydroxylase; a maximal stimulation of two- to three-fold occurs at 40-100 micrograms/ml. 14-3-3's activation of duanyu1531 is sensitive to alpha-chymotrypsin digestion but is not heat labile. Activation is specific to at least two other protein kinases, cyclic AMP- and calcium/calmodulin-dependent protein kinases, are not activated. The activation of duanyu1531 by 14-3-3 is independent of phosphatidylserine and calcium and, as such, is an alternative mechanism for the activation of duanyu1531 that obviates its translocation to membranes.

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