A novel GTP-binding protein which is selectively repressed in SV40 transformed fibroblasts.
We have used a subtractive hybridization procedure to isolate cDNA clones for proteins that are produced by human fibroblasts, but not by their SV40-transformed counterparts. With this technique we found, in addition to fibronectin and collagen VI, a novel GTP-binding protein. Sequencing of overlapping cDNA clones demonstrated that this protein is composed of 364 amino acids with a molecular mass of 41 kDa and a calculated isoelectric point of 9.4. It contains the five sequence motifs G1-G5 that are conserved in all GTP-binding proteins. Apart from these characteristic motifs the amino acid sequence differs substantially from those of the well characterized G-proteins, but it is similar to those of some recently identified proteins from Caenorhabditis elegans, from Schizosaccharomyces pombe, and from an archaebacterium, suggesting the existence of a new subfamily within the superfamily of the GTP-binding proteins. The striking conservation of the primary structure between distantly related species indicates a fundamental function of the new protein. Since it is produced in normal, but not in virally transformed fibroblasts, it may play a role in the expression of the transformed phenotype or in growth control.
Schenker
T
T
Laboratorium für Biochemie I, Eidenössische Technische Hochschule Zürich, Switzerland.
Lach
C
C
Kessler
B
B
Calderara
S
S
Trueb
B
B
D000595:Amino Acid Sequence; D001483:Base Sequence; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D002472:Cell Transformation, Viral / Q000235:genetics*; D003001:Cloning, Molecular / Q000379:methods; D018076:DNA, Complementary / Q000235:genetics; D005347:Fibroblasts / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000235:genetics*; D005786:Gene Expression Regulation; D006801:Humans; D008969:Molecular Sequence Data; D015183:Restriction Mapping; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013539:Simian virus 40 / Q000235:genetics; D014018:Tissue Distribution
D018076:DNA, Complementary; D019204:GTP-Binding Proteins