RhoBTB
Encyclopedia
The RhoBTB family is a subgroup of the Rho family
of small GTPase
s. They are a highly divergent class and are all characterized by an N-terminal Rho-related domain followed by at least one C-terminal BTB domain
.
s looking for cDNAs that cross-hybridize with a very conservative probe from hRas. They identified 19 new genes
that belonged to the Ras superfamily and sequenced approximately 600 nucleotides from the start of the transcript. If they were looking for a normal Ras-like GTPase, this would have been sufficient. One of their clones, they called RacA, was more divergent than most of the others and the transcript didn’t terminate in a stop codon like the rest. The authors, however, didn’t comment on this and RhoBTB went undiscovered for another eight years.
A very careful analysis by Francisco Rivero and coworkers ensued to find all of the Rho GTPases in Dictyostelium. During their endeavor, they found that the open reading frame of RacA was actually 400 amino acids longer than what Bush had published 8 years earlier. Instead of an 168 amino acid protein, RacA encoded a 598 residue protein with a Rho GTPase domain at the N-terminus and two BTB domains toward the C-terminus. BTB (Broad-Complex, Tramtrack and Bric-a-Brac) domains are known to involve hetero and homo associations with other BTB domain-containing proteins. Because this novel RhoBTB protein was in Dictostelium, the authors were curious if any homologous proteins exist in humans. They found three and called them RhoBTB1
, RhoBTB2
, and RhoBTB3
.
RhoBTB1 and 2 were not detected during mouse development, but RhoBTB3 was detected strongly between embryonic days 11.5 through 17.5. Additionally, RhoBTB1 and 2 are localized to vesicular structures, while RhoBTB3 is localized to the trans-Golgi network.
Rho family of GTPases
The Rho family of GTPases is a family of small signaling G protein , and is a subfamily of the Ras superfamily. The members of the Rho GTPase family have been shown to regulate many aspects of intracellular actin dynamics, and are found in all eukaryotic organisms including yeasts and some plants...
of small GTPase
GTPase
GTPases are a large family of hydrolase enzymes that can bind and hydrolyze guanosine triphosphate . The GTP binding and hydrolysis takes place in the highly conserved G domain common to all GTPases.-Functions:...
s. They are a highly divergent class and are all characterized by an N-terminal Rho-related domain followed by at least one C-terminal BTB domain
BTB/POZ domain
The BTB/POZ domain is a common structural domain contained within some proteins.The BTB or POZ domain is present near the N-terminus of a fraction of zinc finger proteins and in proteins that contain the Kelch motif and a family of pox virus proteins...
.
Discovery
The RhoBTB family of molecules was unknowingly discovered in 1993 by analyzing the Dictyostelium genome looking for members of the Ras superfamily of GTPases. The authors began by doing Southern blotSouthern blot
A Southern blot is a method routinely used in molecular biology for detection of a specific DNA sequence in DNA samples. Southern blotting combines transfer of electrophoresis-separated DNA fragments to a filter membrane and subsequent fragment detection by probe hybridization. The method is named...
s looking for cDNAs that cross-hybridize with a very conservative probe from hRas. They identified 19 new genes
Gênes
Gênes is the name of a département of the First French Empire in present Italy, named after the city of Genoa. It was formed in 1805, when Napoleon Bonaparte occupied the Republic of Genoa. Its capital was Genoa, and it was divided in the arrondissements of Genoa, Bobbio, Novi Ligure, Tortona and...
that belonged to the Ras superfamily and sequenced approximately 600 nucleotides from the start of the transcript. If they were looking for a normal Ras-like GTPase, this would have been sufficient. One of their clones, they called RacA, was more divergent than most of the others and the transcript didn’t terminate in a stop codon like the rest. The authors, however, didn’t comment on this and RhoBTB went undiscovered for another eight years.
A very careful analysis by Francisco Rivero and coworkers ensued to find all of the Rho GTPases in Dictyostelium. During their endeavor, they found that the open reading frame of RacA was actually 400 amino acids longer than what Bush had published 8 years earlier. Instead of an 168 amino acid protein, RacA encoded a 598 residue protein with a Rho GTPase domain at the N-terminus and two BTB domains toward the C-terminus. BTB (Broad-Complex, Tramtrack and Bric-a-Brac) domains are known to involve hetero and homo associations with other BTB domain-containing proteins. Because this novel RhoBTB protein was in Dictostelium, the authors were curious if any homologous proteins exist in humans. They found three and called them RhoBTB1
RHOBTB1
Rho-related BTB domain-containing protein 1 is a protein that in humans is encoded by the RHOBTB1 gene.-Further reading:...
, RhoBTB2
RHOBTB2
Rho-related BTB domain-containing protein 2 is a protein that in humans is encoded by the RHOBTB2 gene.-Further reading:...
, and RhoBTB3
RHOBTB3
Rho-related BTB domain-containing protein 3 is a protein that in humans is encoded by the RHOBTB3 gene.-Further reading:...
.
Localization and expression
RhoBTB1 and RhoBTB2 are much more homologous than RhoBTB3. Further analysis revealed that the intron-exon structure of RhoBTB1 and 2 are also quite similar and have only one common intron with RhoBTB3.RhoBTB1 and 2 were not detected during mouse development, but RhoBTB3 was detected strongly between embryonic days 11.5 through 17.5. Additionally, RhoBTB1 and 2 are localized to vesicular structures, while RhoBTB3 is localized to the trans-Golgi network.