PURIFICATION, CHARACTERIZATION, AND IN-VITRO PHOSPHORYLATION OF THE NEURON-SPECIFIC MEMBRANE-ASSOCIATED PROTEIN SCG10

SCG10 is a neuron-specific, developmentally regulated protein which is highly enriched in growth cones. Sequence homology indicates that it is related to the phosphoprotein stathmin or Op18, an in vitro and in vivo substrate for several serine/threonine kinases which are involved in a variety of signaling pathways. As a first step to examine the bi ochemical properties of SCG10, the protein was expressed in Escherichi a coil and purified to apparent homogeneity. The purified protein was used in in vitro phosphorylation assays. SCG10 was phosphorylated by M AP kinase, cAMP-dependent protein kinase, cGMP-dependent protein kinas e, p34(cdc2) kinase, DNA-dependent protein kinase, Ca2+/calmodulin kin ase II, and casein kinase II. The protein was not a substrate for case in kinase I and protein kinase C. SCG10 was phosphorylated by src tyro sine kinase, which demonstrates that the protein can be phosphorylated in vitro on a tyrosine residue. Our data suggest that SCG10 is a phos phoprotein which might be involved in signal transduction in neurons. (C) 1997 Academic Press.