Observation of Continuous Contraction and a Metastable Misfolded State during the Collapse and Folding of a Small Protein

Bhatia, S and Krishnamoorthy, G and Dhar, D and Udgaonkar, JB (2019) Observation of Continuous Contraction and a Metastable Misfolded State during the Collapse and Folding of a Small Protein. In: Journal of Molecular Biology, 431 (19). pp. 3814-3826.

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Abstract

To obtain proper insight into how structure develops during a protein folding reaction, it is necessary to understand the nature and mechanism of the polypeptide chain collapse reaction, which marks the initiation of folding. Here, the time-resolved fluorescence resonance energy transfer technique, in which the decay of the fluorescence light intensity with time is used to determine the time evolution of the distribution of intra-molecular distances, has been utilized to study the folding of the small protein, monellin. It is seen that when folding begins, about one-third of the protein molecules collapse into a molten globule state (IMG), from which they relax by continuous further contraction to transit to the native state. The larger fraction gets trapped into a metastable misfolded state. Exit from this metastable state occurs via collapse to the lower free energy IMG state. This exit is slow, on a time scale of seconds, because of activation energy barriers. The trapped misfolded molecules as well as the IMG molecules contract continuously and slowly as structure develops. A phenomenological model of Markovian evolution of the polymer chain undergoing folding, incorporating these features, has been developed, which fits well the experimentally observed time evolution of distance distributions. The observation that the “wrong turn” to the misfolded state has not been eliminated by evolution belies the common belief that the folding of functional protein sequences is very different from that of a random heteropolymer, and the former have been selected by evolution to fold quickly.

Item Type:	Journal Article
Publication:	Journal of Molecular Biology
Publisher:	Academic Press
Additional Information:	The copyright for this article belongs to Academic Press.
Keywords:	monellin; polymer; polypeptide; monellin protein, Dioscoreophyllum cumminsii; peptide; plant protein, Article; controlled study; enzyme activation; enzyme mechanism; fluorescence resonance energy transfer; light intensity; Markov chain; molecular dynamics; phenomenology; polymerase chain reaction; priority journal; protein analysis; protein function; protein localization; protein misfolding; protein structure; chemistry; kinetics; metabolism; probability; protein denaturation; protein folding; protein stability, Kinetics; Markov Chains; Molecular Dynamics Simulation; Peptides; Plant Proteins; Probability; Protein Denaturation; Protein Folding; Protein Stability
Department/Centre:	Division of Biological Sciences > Microbiology & Cell Biology
Date Deposited:	06 Jan 2023 06:15
Last Modified:	06 Jan 2023 06:15
URI:	https://eprints.iisc.ac.in/id/eprint/78805

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