Figure 1.

Kinase and Binding Activities of PK12 Fusion Proteins.

(A) In vitro kinase assay of PK12 fusion proteins. PK12:GFP and its mutant forms were immunoprecipitated from transgenic BY-2 cells using antibodies raised against GFP. Nontransformed cells (wild type) were used as a control. The immunoprecipitate was subjected to an in vitro kinase assay using atSRp34/SR1 (top) or MBP (bottom) as a substrate.

(B) In vitro kinase assay of recombinant PK12 protein using atSRp34/SR1 as a substrate. Myc:SR1 was immunoprecipitated from control and transgenic BY-2 cells and subjected to an in vitro kinase assay in the presence or absence of recombinant GST:PK12. Residual autophosphorylation activity of the latter is shown.

(C) Overlay assay. atSRp34/SR1 and MBP proteins (1 μg) were fractionated on an SDS–polyacrylamide gel and transferred to a nitrocellulose membrane. The membrane then was probed with in vitro Met ³⁵S- labeled PK12:GFP.