THE IDENTIFICATION OF A COMPLEX FAMILY OF LOW-MOLECULAR-WEIGHT GTP-BINDING PROTEIN HOMOLOGS FROM PARAMECIUM-TETRAURELIA BY PCR CLONING

We have used the polymerase chain reaction to clone a large number of gene fragments encoding low-molecular-weight GTP-binding proteins (LMW G-proteins) from Paramecium tetraurelia. All clones were subjected to a computer-assisted search of the GenBank databases to assign putative homologues. On the basis of several conserved features, we place these genes in the rab/ypt and rho subfamilies of the LMW G-proteins. Northern blot analyses indicated that all clones were from active genes. One surprising feature of the cloned genomic sequences was the presence of unusually short introns (20-30 nucleotides).