TitleMicrosecond rearrangements of hydrophobic clusters in an initially collapsed globule prime structure formation during the folding of a small protein.
Publication TypeJournal Article
Year of Publication2016
AuthorsGoluguri RReddy, Udgaonkar JB
JournalJ Mol Biol
Date Published2016 Jun 28

To determine how polypeptide chain collapse initiates structure formation during protein folding is a long standing goal. It has been challenging to characterize experimentally the dynamics of the polypeptide chain which lead to the formation of a compact kinetic molten globule (MG) in about a millisecond. In this study, the sub-millisecond events that occur early during the folding of monellin (MNEI) from the guanidine hydrochloride-unfolded state have been characterized using multiple fluorescence and fluorescence resonance energy transfer probes. The kinetic MG is shown to form in a non-cooperative manner from the unfolded (U) state as a result of at least three different processes happening during the first millisecond of folding. Initial chain compaction completes within the first 37μs, and further compaction occurs only after structure formation commences at a few milliseconds of folding. Transient non-native and native-like hydrophobic clusters with side-chains of certain residues buried form during the initial chain collapse, and the non-native clusters quickly disassemble. Subsequently, partial chain-desolvation occurs, leading to the formation of a kinetic MG. The initial chain compaction and subsequent chain rearrangement appear to be barrier-less processes. The two structural rearrangements within the collapsed globule appear to prime the protein for the actual folding transition.

Alternate JournalJ. Mol. Biol.
PubMed ID27370109