PURIFICATION OF LOW-MOLECULAR-WEIGHT GTP-BINDING PROTEINS STRUCTURALLY RELATED TO MTG33, A MITOCHONDRIAL GTP-BINDING PROTEIN OF EHRLICH ASCITES TUMOR-CELLS

We purified a mitochondrial GTP-binding protein, MTG33, from a particu late fraction of Ehrlich ascites tumor cells [Takeda, S., Sagara, Y., Kita, K., Natori, S., and Sekimizu, K. (1993) J. Biochem. 114, 684-690 ]. In the present work, three GTP-binding proteins, p23A, p23B, and p2 6, were purified from the same material. The K-d values of p23A, p23B, and p26 for GTP were 19, 6.8, and 4.0 nM, respectively. Binding of [a lpha-P-32]GTP to these proteins was inhibited by GTP and GDP, but not appreciably by other nucleotides such as ATP, CTP, UTP, and GMP. p23A, p23B, and p26 hydrolyzed G;TP to GDP as well as MTG33 did. Peptide ma pping analyses revealed that these GTP-binding proteins share common p rimary structures with MTG33. The defined properties of the three prot eins suggest structural and functional relations to MTG33, which is lo calized in mitochondria.