Catalyzes the transfer of a geranylgeranyl moiety from geranylgeranyl diphosphate to both cysteines of Rab proteins with the C-terminal sequence -XXCC, -XCXC and -CCXX, such as RAB1A, RAB3A, RAB5A and RAB7A. (updated: March 4, 2015)
The data and differentiation stages presented below come from the proteomic study and analysis performed by our partners of the GReX consortium, more details are available in their published work.
No sequence conservation computed yet.
This protein is annotated as membranous in Gene Ontology.
Total structural coverage: 100%
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The reference OMIM entry for this protein is 179080
Rab geranylgeranyl transferase, beta subunit; rabggtb
Rab geranylgeranyltransferase, beta component
Gg transferase, component b; ggtb
CLONING
By sequencing clones from a Burkitt lymphoma cDNA library, Sanders et al. (1996) cloned RABGGTB. The cDNA showed 82.4% identity over 341 bp of coding sequence to a rat sequence encoding the catalytic subunit of RAB geranylgeranyl transferase. The amino acid sequences of the 2 genes are 91.1% similar. Van Bokhoven et al. (1996) cloned the complete human cDNA of RABGGTB from a fetal brain library and reported that it encodes a 331-amino acid polypeptide, which is very well conserved among both mammalian and lower eukaryotic species. Wei et al. (1995) found that Rabggtb is ubiquitously expressed in adult mice, but displays a varying pattern of expression during embryonic development. Its expression was detected in whole embryos during early embryonic stages, but was specifically concentrated in the developing brain, heart, and liver during gestation stages E11.5 and E13.5.
GENE FUNCTION
Seabra et al. (1991) presented evidence that 2 prenyltransferases, farnesyltransferase and geranylgeranyltransferase, are heterodimers that share a common alpha subunit with different beta subunits. Three distinct prenyltransferases attach polyisoprene units in thioether linkage to cysteine residues of membrane-bound cellular proteins. The best-characterized enzyme, protein farnesyltransferase, attaches 15 carbon farnesyl units to cysteine residues at the fourth position from the C-terminus of p21(ras) proteins, nuclear lamins, and other proteins that end in the so-called CAAX box, where C is cysteine, A is usually but not always an aliphatic amino acid, and X is methionine or serine. The CAAX farnesyltransferase is a tightly coupled heterodimer composed of a 49-kD alpha subunit (RABGGTA;
601905) and a 46-kD beta subunit. The other 2 known prenyltransferases transfer 20 carbon geranylgeranyl groups. One of these enzymes resembles the CAAX farnesyltransferase (FNTA;
134635) in recognizing a C-terminal CAAX box. Instead of methionine or serine, the CAAX geranylgeranyl transferase (GG transferase) prefers leucine. The third identified prenyltransferase is a GG transferase that recognizes proteins that terminate in the sequence cys-X-cys or cys-cys. Its substrates include a large family of related membrane-associated GTP-binding proteins termed RAB proteins. The enzyme from rat brain contains 2 components, A and B. Component B comprises polypeptides of 60 and 38 kD. Seabra et al. (1992) hypothesized that component A binds conserved sequences in RAB and that component B transfers geranylgeranyl.
MAPPING
Sanders et al. (1996) probed a genomic Southern blot from a panel of 24 interspecies somatic cell hybrids and localized the gene to human chromosome 1; a much fainter band was also present in the chromosome 3 somatic cell hybrid, pointing to the existence of a related gene on that chromosome. By fluorescence in situ hybridization they further localized the gene to chromosome 1p31-p22. Van Bokhoven et al. (1996) refined the mapping of the RAGGTB gene to chromosome 1p31 using fluorescence in situ hybridization. Wei et al. (1995) mapped the mouse homolog to the distal region of mouse chromosome 3. ...
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Feb. 2, 2018: Protein entry updated
Automatic update: Uniprot description updated
Dec. 19, 2017: Protein entry updated
Automatic update: Uniprot description updated
Nov. 23, 2017: Protein entry updated
Automatic update: Uniprot description updated
June 20, 2017: Protein entry updated
Automatic update: comparative model was added.
March 16, 2016: Protein entry updated
Automatic update: OMIM entry 179080 was added.