Cloning of cDNAs encoding a cell-cycle-regulatory GTP-binding low-M(r) (GBLM) protein, Ran/TC4, from micronucleated Tetrahymena thermophila and amicronucleated Tetrahymena pyriformis.
Using PCR we have isolated two novel, closely related cDNA clones coding for a GTP-binding low-M(r) protein from Tetrahymena cells. The two clones from T. thermophila and T. pyriformis have open reading frames encoding proteins of 225 amino acids (aa) with a calculated M(r) of 25,648, and of 223 aa with a calculated M(r) of 25,421, respectively. The two gene products were very homologous to Ran/TC4 which are involved in chromatin condensation and control of the cell cycle: they possess much higher similarities to human, chicken, Schizosaccharomyces pombe and Dictyostelium discoideum Ran/TC4 homologues than those to other GTP-binding low-M(r) proteins, such as Ras and Rho. Thus, the two clones isolated from Tetrahymena were designated as Tt-ran and Tp-ran, respectively. Tt-ran and Tp-ran share 83% identity at nucleotide level, and about 92% identity and 94% homology at aa level. Tt- and Tp-Ran, as well as other Ran/TC4, contain the four consensus regions involved in GTP/GDP-binding and GTPase activities. However, at the C-terminal end, although all the known Ran/TC4 terminate in a consensus D-L motif, Tt-Ran and Tp-Ran do not have the unique aa sequence of other Ran/TC4, but have a F-N motif. Tt-ran and Tp-ran were actively transcribed in vivo as a 1.0-kb mRNA.
Department of Biochemistry, Gifu University School of Medicine, Japan.
K
K
Nagata
T
T
Takemasa
S
S
Alam
T
T
Hattori
Y
Y
Watanabe
Y
Y
Nozawa
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002453:Cell Cycle / Q000235:genetics; D003001:Cloning, Molecular; D018076:DNA, Complementary; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics*; D048631:Micronucleus, Germline; D008969:Molecular Sequence Data; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013769:Tetrahymena pyriformis / Q000235:genetics* / Q000648:ultrastructure; D016808:Tetrahymena thermophila / Q000235:genetics* / Q000648:ultrastructure
D018076:DNA, Complementary; D015800:Protozoan Proteins; D019204:GTP-Binding Proteins