Direct photoaffinity labeling of soluble GTP‐binding proteins in Dictyostelium discoideum

Abstract
Major cytoplasmic GTP‐binding proteins in Dictyostelium discoideum were identified by direct photoaffinity labeling with [α‐32P]GTP. Three actin‐binding proteins and a protein with an apparent molecular mass of 24 kDa (p24) could be labeled with [α‐32P]GTP. p24 binds to DEAE‐cellulose, behaves like a monomer during gel filtration and was purified to homogeneity by GTP‐affinity chromatography. In comparison to other nucleotide triphosphates the binding of GTP to p24 is highly specific.