title: Effect of macromolecular crowding on protein folding dynamics at the secondary structure level.
abstract: Macromolecular crowding is one of the key characteristics of the cellular environment and is therefore intimately coupled to the process of protein folding in vivo. While previous studies have provided invaluable insight into the effect of crowding on the stability and folding rate of protein tertiary structures, very little is known about how crowding affects protein folding dynamics at the secondary structure level. In this study, we examined the thermal stability and folding-unfolding kinetics of three small folding motifs (i.e., a 34-residue alpha-helix, a 34-residue cross-linked helix-turn-helix, and a 16-residue beta-hairpin) in the presence of two commonly used crowding agents, Dextran 70 (200 g/L) and Ficoll 70 (200 g/L). We found that these polymers do not induce any appreciable changes in the folding kinetics of the two helical peptides, which is somewhat surprising as the helix-coil transition kinetics have been shown to depend on viscosity. Also to our surprise and in contrast to what has been observed for larger proteins, we found that crowding leads to an appreciable decrease in the folding rate of the shortest beta-hairpin peptide, indicating that besides the excluded volume effect, other factors also need to be considered when evaluating the net effect of crowding on protein folding kinetics. A model considering both the static and the dynamic effects arising from the presence of the crowding agent is proposed to rationalize these results.
authors.affiliation: Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, PA 19104, USA.
authors.forename: Smita
authors.initials: S
authors.lastname: Mukherjee
authors.forename: Matthias M
authors.initials: MM
authors.lastname: Waegele
authors.forename: Pramit
authors.initials: P
authors.lastname: Chowdhury
authors.forename: Lin
authors.initials: L
authors.lastname: Guo
authors.forename: Feng
authors.initials: F
authors.lastname: Gai
mesh_terms: D002942:Circular Dichroism; D007700:Kinetics; D009842:Oligopeptides / Q000737:chemistry* / Q000378:metabolism*; D017510:Protein Folding; D055550:Protein Stability; D017433:Protein Structure, Secondary; D013696:Temperature; D014783:Viscosity
chemical_list: D009842:Oligopeptides
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