Molecular crowding impacts the structure of apolipoprotein A-I with potential implications on in vivo metabolism and function
Jitka Petriova, Silvia Hilt, Madhu Budamagunta, Joan Domingo-Espín, John C Voss, Jens O Lagerstedt
We have explored the effect molecular crowding, defined as the volume exclusion exerted by one soluble inert molecule upon another soluble molecule, has on the structure and self-interaction of lipid-free apoA-I. The influence of molecular crowding on lipid-free apoA-I oligomerization and internal dynamics has been analyzed using electron paramagnetic resonance (EPR) spectroscopy measurements of nitroxide spin label at selected positions throughout the protein sequence and at varying concentrations of the crowding agent Ficoll-70. The targeted positions include sites previously shown to be sensitive for detecting intermolecular interaction via spin-spin coupling. Circular dichroism was used to study secondary structural changes in lipid-free apoA-I imposed by increasing concentrations of the crowding agent. Crosslinking and SDS-PAGE gel analysis was employed to further characterize the role molecular crowding plays in inducing apoA-I oligomerization. We conclude that the dynamic apoA-I structure and oligomeric state is altered in the presence of the crowding agent. We also find that the C-terminal is slightly more sensitive to molecular crowding. Finally, our data describes the region around residue 217 in the C-terminal domain of apoA-I as the most sensitive reporter of the crowding-induced self-association of apoA-I. The implications of this behavior to in vivo functionality are discussed.
Circular dichroism, Secondary structure, Ligand binding, Biochemistry, Medicinal