About GDI / GDP Dissociation Inhibitor:
The C-terminal, known as geranylgeranylation, is a vital mechanism for the proper function of the GDI and its association. It is a post-translational modification catalysed by the Rab enzyme, also known as geranylgeranyl transferase (Rab-GGTase).
GDI Structure
The Rab Escort protein, as it is colloquially known, is an enzyme that contains a catalytic heterodimer and an accessory component. It presents newly synthesised Rab proteins to the catalytic component to form stable complex prenylated proteins.
The structure of the Rab GDI protein is crystal. It has a resolution of 1.81 Angstrom. It is typically composed of two parts, a large and complex multi-sheet domain and a smaller alpha, helical domain. The most important part of the structure is the apex of the molecule, which plays a crucial role in the binding of Rab proteins.
GDP Dissociation Inhibitor Mechanism
The Rab GDP dissociation inhibitor is similar to the mechanism of the REP-1 mediated membrane association of Rab 5. This pair of inhibitors share other properties, too, like their ability to inhibit the release of GDP and to remove Rab protein and membranes. Like most proteins, the Rab GDP doesn't function alone and interacts with molecular machines made of numerous content proteins.
GDI Function
GDP dissociation inhibitors regulate the exchange reaction of members of the Rab family. They are small binding proteins involved in the vesicular trafficking of molecules between organelles.
Rab GTPases is crucial to the exchange. It cycles between the cytosolic compartment and the membrane. It is bound to a protein in the compartment and interacts with a receptor in the exchange to catalyse the process.