Binds unprenylated Rab proteins, presents it to the catalytic Rab GGTase dimer, and remains bound to it after the geranylgeranyl transfer reaction. The component A is thought to be regenerated by transferring its prenylated Rab back to the donor membrane. Also a pre-formed complex consisting of CHM and the Rab GGTase dimer (RGGT or component B) can bind to and prenylate Rab proteins; this alternative pathway is proposed to be the predominant pathway for Rab protein geranylgeranylation.
Prenylation (or geranylgeranylation) of Rab GTPases is catalysed by RGGT (Rab geranylgeranyl transferase) and requires REP (Rab escort protein). In the classical pathway, REP associates first with unprenylated Rab, which is then prenylated by RGGT. In the alternative pathway, REP associates first with RGGT; this complex then binds and prenylates Rab proteins. In the present paper we show that REP mutants defective in RGGT binding (REP1 F282L and REP1 F282L/V290F) are unable to compete with wild-type REP in the prenylation reaction in vitro. When over-expressed in cells, REP wild-type and mutants are unable to form stable cytosolic complexes with endogenous unprenylated Rabs. These results suggest that the alternative pathway may predominate in vivo. We also extend previous suggestions that GGPP (geranylgeranyl pyrophosphate) acts as an allosteric regulator of the prenylation reaction. We observed that REP-RGGT complexes are formed in vivo and are unstable in the absence of intracellular GGPP. RGGT increases the ability of REP to extract endogenous prenylated Rabs from membranes in vitro by stabilizing a soluble REP-RGGT-Rab-GG (geranylgeranylated Rab) complex. This effect is regulated by GGPP, which promotes the dissociation of RGGT and REP-Rab-GG to allow delivery of prenylated Rabs to membranes.
Catalysis of the reaction: 2 geranylgeranyl diphosphate + protein-cysteine = 2 S-geranylgeranyl-protein + 2 diphosphate. This reaction is the formation of two thioether linkages between the C-1 atom of the geranylgeranyl groups and two cysteine residues within the terminal sequence motifs XXCC, XCXC or CCXX. Known substrates include Ras-related GTPases of a single family and the Rab family.
The process whose specific outcome is the progression of a blood vessel over time, from its formation to the mature structure. The blood vessel is the vasculature carrying blood.
The directed movement of proteins in a cell, including the movement of proteins between specific compartments or structures within a cell, such as organelles of a eukaryotic cell.
Rab geranylgeranyl transferase (GG transferase) is a two-component enzyme that attaches 20-carbon isoprenoid groups to cysteine residues in Rab proteins, a family of guanosine triphosphate-binding proteins that regulate vesicular traffic. The mutant gene in human choroideremia, an X-linked form of retinal degeneration, encodes a protein that resembles component A of rat Rab GG transferase. Lymphoblasts from choroideremia subjects showed a marked deficiency in the activity of component A, but not component B, of Rab GG transferase. The deficiency was more pronounced when the substrate was Rab3A, a synaptic vesicle protein, than it was when the substrate was Rab1A, a protein of the endoplasmic reticulum. The data imply the existence of multiple component A proteins, one of which is missing in choroideremia.
Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a stimulus. The process begins with detection of the stimulus and ends with a change in state or activity or the cell or organism.
The series of events required for an organism to receive a visual stimulus, convert it to a molecular signal, and recognize and characterize the signal. Visual stimuli are detected in the form of photons and are processed to form an image.
Protein involved in sensory transduction, the process by which a cell converts an extracellular signal, such as light, taste, sound, touch or smell, into electric signals.
Protein involved in vision, the special sense by which objects in the external environment are perceived by the light they give off or reflect, which stimulates the photoreceptors in the retina.
A reference proteome is a set of protein sequences derived from a complete proteome which constitutes a defined standard for a particular user community. Reference proteomes are manually defined according to a number of criteria. They cover the proteomes of well- studied model organisms and other proteomes of interest for biomedical and biotechnological research. Reference proteomes have been selected to provide broad coverage of the tree of life, and constitute a representative cross-section of the taxonomic diversity to be found within UniProtKB.
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