Biochemical properties of the YPT‐related <i>rab</i>1B protein

Abstract

We recently identified a novel rat cDNA: rab1B, closely related to the rab1A cDNA and to the yeast YPT1 gene. The rab1B cDNA encodes a 202 amino acid protein (22.1 kDa) that was produced in Escherichia coli under the control of the phi 10 promoter for the T7 RNA polymerase. The rab1B protein was purified in large amounts to near homogeneity in a simplified procedure. We studied the biochemical properties of rab1B and rab1A proteins. They both bind specifically GTP and GDP and possess intrinsic GTPase activities. The rab1B Lys21----Met mutant protein does not bind GTP, whereas the Ala65----Thr mutant has a reduced GTPase activity and is competent for autophosphorylation in the presence of GTP.