title: RhoGDI facilitates geranylgeranyltransferase-I-mediated RhoA prenylation.
abstract: Protein prenylation is a post-translational modification where farnesyl or geranylgeranyl groups are enzymatically attached to a C-terminal cysteine residue. This modification is essential for the activity of small cellular GTPases, as it allows them to associate with intracellular membranes. Dissociated from membranes, prenylated proteins need to be transported through the aqueous cytoplasm by protein carriers that shield the hydrophobic anchor from the solvent. One such carrier is Rho GDP dissociation inhibitor (RhoGDI). Recently, it was shown that prenylated Rho proteins that are not associated with RhoGDI are subjected to proteolysis in the cell. We hypothesized that the role of RhoGDI might be not only to associate with prenylated proteins but also to regulate the prenylation process in the cell. This idea is supported by the fact that RhoGDI binds both unprenylated and prenylated Rho proteins with high affinity in vitro, and hence, these interactions may affect the kinetics of prenylation. We addressed this question experimentally and found that RhoGDI increased the catalytic efficiency of geranylgeranyl transferase-I in RhoA prenylation. Nevertheless, we did not observe formation of a ternary RhoGDI∗RhoA∗GGTase-I complex, indicating sequential operation of geranylgeranyltransferase-I and RhoGDI. Our results suggest that RhoGDI accelerates Rho prenylation by kinetically trapping the reaction product, thereby increasing the rate of product release.
authors.affiliation: Department of Molecular Cell Biology, Institute for Molecular Bioscience, The University of Queensland, 306 Carmody Road, St. Lucia, QLD 4072, Australia.
authors.forename: Zakir
authors.initials: Z
authors.lastname: Tnimov
authors.affiliation: Department of Molecular Cell Biology, Institute for Molecular Bioscience, The University of Queensland, 306 Carmody Road, St. Lucia, QLD 4072, Australia.
authors.forename: Daniel
authors.initials: D
authors.lastname: Abankwa
authors.affiliation: Department of Molecular Cell Biology, Institute for Molecular Bioscience, The University of Queensland, 306 Carmody Road, St. Lucia, QLD 4072, Australia. Electronic address: k.alexandrov@uq.edu.au.
authors.forename: Kirill
authors.initials: K
authors.lastname: Alexandrov
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000378:metabolism*; D000818:Animals; D002384:Catalysis; D002460:Cell Line; D006224:Cricetinae; D005347:Fibroblasts / Q000378:metabolism*; D017368:Protein Prenylation / Q000502:physiology*; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D019883:Alkyl and Aryl Transferases; C083291:geranylgeranyltransferase type-I; D020742:rhoA GTP-Binding Protein
keywords: GGTase-I; Protein prenylation; Rho GTPases; RhoGDI