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Published on: September 21, 2011
Biochemical and kinetic properties of the complex Roco G-protein cycle
Lina Wauters1,2,3, Susanne Terheyden2,4, Bernd K Gilsbach5
1VIB-VUB Center for Structural Biology, Pleinlaan 2, B-1050 Brussels, Belgium.
Abstract:
Roco proteins have come into focus after mutations in the gene coding for the human Roco protein Leucine-rich repeat kinase 2 (LRRK2) were discovered to be one of the most common genetic causes of late onset Parkinson's disease. Roco proteins are characterized by a Roc domain responsible for GTP binding and hydrolysis, followed by a COR dimerization device. The regulation and function of this RocCOR domain tandem is still not completely understood. To fully biochemically characterize Roco proteins, we performed a systematic survey of the kinetic properties of several Roco protein family members, including LRRK2. Together, our results show that Roco proteins have a unique G-protein cycle. Our results confirm that Roco proteins have a low nucleotide affinity in the micromolar range and thus do not strictly depend on G-nucleotide exchange factors. Measurement of multiple and single turnover reactions shows that neither Pi nor GDP release are rate-limiting, while this is the case for the GAP-mediated GTPase reaction of some small G-proteins like Ras and for most other high affinity Ras-like proteins, respectively. The KM values of the reactions are in the range of the physiological GTP concentration, suggesting that LRRK2 functioning might be regulated by the cellular GTP level.
Insights
Roco proteins, including Leucine-rich repeat kinase 2 (LRRK2), exhibit a unique G-protein cycle with low nucleotide affinity. Their function may be regulated by cellular GTP levels, offering insights into Parkinson's disease.
Area of Science:
- Biochemistry
- Molecular Biology
- Neuroscience
Background:
- Mutations in Leucine-rich repeat kinase 2 (LRRK2) are a common cause of late-onset Parkinson's disease.
- Roco proteins, including LRRK2, possess a Roc domain for GTP binding/hydrolysis and a COR dimerization domain, but their regulation is unclear.
Purpose of the Study:
- To biochemically characterize the kinetic properties of Roco proteins, including LRRK2.
- To elucidate the unique G-protein cycle and regulatory mechanisms of Roco proteins.
Main Methods:
- Systematic survey of kinetic properties of Roco protein family members.
- Measurement of multiple and single turnover reactions.
- Analysis of GTP binding and hydrolysis rates.
Main Results:
- Roco proteins demonstrate a unique G-protein cycle with low nucleotide affinity (micromolar range).
- Nucleotide exchange factors are not strictly required for Roco protein function.
- Pi and GDP release are not rate-limiting steps; GTPase reaction is distinct from small G-proteins like Ras.
- KM values suggest cellular GTP concentration may regulate LRRK2 activity.
Conclusions:
- Roco proteins possess a distinct G-protein regulatory mechanism.
- LRRK2's enzymatic activity is potentially modulated by physiological GTP levels.
- Understanding Roco protein biochemistry provides insights into Parkinson's disease pathogenesis.
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