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Single prenyl-binding site on protein prenyl transferases
1Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75235, USA.
Summary
Protein prenyl transferases, including Rab geranylgeranyl transferase (RabGGTase), function as prenyl carriers. This study reveals RabGGTase has a single prenyl-binding site, transferring two geranylgeranyl groups to Rab proteins sequentially.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Background:
- Three enzymes, FTase, GGTase-I, and RabGGTase, catalyze protein prenylation.
- CAAX motif proteins are prenylated by FTase or GGTase-I.
- Rab proteins are prenylated by RabGGTase via a double-cysteine motif.
Purpose of the Study:
- To investigate the prenyl carrier function of RabGGTase.
- To determine the stoichiometry of enzyme:prenyl pyrophosphate complexes.
- To elucidate the mechanism of Rab protein prenylation.
Main Methods:
- Development of a prenyl-binding assay.
- Characterization of stable enzyme:prenyl pyrophosphate complexes.
- Single turnover reactions and chromatographic analysis of prenylated products.
Main Results:
- RabGGTase exhibits prenyl carrier function, forming stable 1:1 complexes with GGPP.
- FTase and GGTase-I also form stable 1:1 complexes with GGPP.
- Rab proteins are mono-geranylgeranylated in single turnover reactions by RabGGTase.
Conclusions:
- All three protein prenyl transferases possess a single prenyl-binding site.
- RabGGTase likely transfers two geranylgeranyl groups to Rab proteins in consecutive reactions.
- This finding clarifies the mechanism of Rab protein prenylation.