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Exploring structural aspects of the human Golgi matrix protein GRASP55 in solution
S Thirupathi Reddy1, Luis Felipe Santos Mendes1, Natalia Aparecida Fontana1
1Department of Physics, Ribeirão Preto School of Philosophy, Science and Literature, University of Sao Paulo, Av. Bandeirantes 3900, 14040-901 Ribeirão Preto, SP, Brazil.
International Journal of Biological Macromolecules
|May 19, 2019
Summary
Golgi reassembly and stacking proteins (GRASPs) like GRASP55 are crucial for Golgi organization and protein secretion. This study reveals GRASP55 forms amorphous aggregates in an intermediate state, offering insights into its function.
Area of Science:
- Cell Biology
- Biochemistry
- Structural Biology
Background:
- The Golgi apparatus is vital for protein and lipid processing and trafficking.
- Golgi reassembly and stacking proteins (GRASPs) are implicated in Golgi structure and unconventional protein secretion.
- The precise structural mechanisms of GRASP function remain unclear.
Purpose of the Study:
- To investigate the biochemical and biophysical properties of human full-length GRASP55 in solution.
- To elucidate the structural behavior of GRASP55 under different conditions.
- To provide insights into the role of GRASP55 in Golgi organization and protein secretion.
Main Methods:
- Sequence-based analyses
- Circular dichroism spectroscopy
- Size exclusion chromatography and multiple-angle light scattering
- Urea denaturation
- Differential scanning calorimetry
- Thioflavin T fluorescence
- Transmission electron microscopy
- Fluorescence lifetime imaging microscopy
Main Results:
- GRASP55 exhibits intrinsically disordered regions alongside regular secondary structures.
- GRASP55 exists as monomers in solution.
- Urea denaturation indicates a cooperative unfolding process with a distinct intermediate state.
- Differential scanning calorimetry reveals two transitions, suggesting an intermediate state.
- The intermediate state of GRASP55 forms amorphous aggregates, not amyloid-like fibrils.
Conclusions:
- Human GRASP55 displays complex structural properties in solution, including aggregation.
- The identified intermediate state and aggregation behavior may be relevant to GRASP55's role in Golgi organization.
- Understanding GRASP55's structural dynamics can illuminate its function in unconventional protein secretion.
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