Rab11a is modified in vivo by isoprenoid geranylgeranyl.
Post-translational adduction of farnesyl or geranylgeranyl moieties to a terminal cysteine residue of proteins is a characteristic feature of ras-related GTP-binding proteins. According to current rules of prenylation, the carboxyl-terminal motif (CXXX or CC/CXC) as well the context of the cysteine residue dictate the extend and specificity of the isoprenoid modification. Rablla, a small GTP-binding protein that is associated with pathways regulating protein traffic, terminates with isoleucine at its C-terminus, suggesting that it may only be geranylgeranylated. Recent finding, however, showed that rab11a can be modified in vitro by different prenyl groups: farnesyl and geranylgeranyl [1]. To determine whether rablla is modified in vivo by both isoprenoids we transiently overexpressed rablla in COS1 cells, and analyzed the translation products by two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) in combination with metabolic labeling in the presence of either [3H]farnesyl-PP or [3H]geranylgeranyl-PP. Contrary to the in vitro results, our studies showed that rab11a is post-translationally modified in vivo only by geranylgeranyl isoprenoid. The data implied that in vivo there must exist other determinant(s) that are necessary for prenyltransferase recognition.
Department of Medical Biochemistry and Danish Centre for Human Genome Research, Aarhus University. gromov@biobase.dk
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D000818:Animals; D019556:COS Cells; D015180:Electrophoresis, Gel, Two-Dimensional; D019204:GTP-Binding Proteins / Q000032:analysis* / Q000235:genetics; D015870:Gene Expression; D017368:Protein Prenylation; D020691:rab GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins
D019204:GTP-Binding Proteins; D020691:rab GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins