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Ultrafast events in the folding of ferrocytochrome c.
Biochemistry. 2005 Jul 05; 44(26):9359-67.B

Abstract

Laser flash photolysis and stopped-flow methods have been used to study the dynamic events in the micro- to millisecond time bin in the refolding of horse ferrocytochrome c in the full range of guanidine hydrochloride concentration at pH 12.8 (+/-0.1), 22 degrees C. Under the absolute refolding condition, the earliest relaxation time of the unfolded protein chain is less than 1 micros. The chain then undergoes diffusive dynamics-mediated contraction and expansion, in which intrapolypeptide ligands make transient contacts with the heme iron, giving rise to two distinct kinetic phases of approximately 0.4 and approximately 3 micros. Under moderate to absolute refolding conditions, the rates of these processes show little dependence on the denaturant concentration, indicating the absence of structural element in the incipient or the relaxed state. Chain expansion and contraction events continue until the polypeptide finds a stable and supportive transition state. The crossing of this transition barrier, which rate-limits the folding of alkaline ferrocytochrome c, is characterized by a stopped-flow measured time constant of approximately 3 ms in aqueous solvent. Observed kinetics thus implicate no submillisecond folding structure. The folding kinetics is effectively two state in which the unfolded polypeptide first relaxes to an unstructured chain and then crosses over a late rate-limiting barrier to achieve the native conformation. The experimentally observed rates as a function of guanidine hydrochloride concentration have been simulated by numerically calculated microscopic rates of a simple kinetic model that captures the essential features of folding.

Authors+Show Affiliations

School of Chemistry, University of Hyderabad, Hyderabad 500046, India.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

15982002

Citation

Kumar, Rajesh, et al. "Ultrafast Events in the Folding of Ferrocytochrome C." Biochemistry, vol. 44, no. 26, 2005, pp. 9359-67.
Kumar R, Prabhu NP, Bhuyan AK. Ultrafast events in the folding of ferrocytochrome c. Biochemistry. 2005;44(26):9359-67.
Kumar, R., Prabhu, N. P., & Bhuyan, A. K. (2005). Ultrafast events in the folding of ferrocytochrome c. Biochemistry, 44(26), 9359-67.
Kumar R, Prabhu NP, Bhuyan AK. Ultrafast Events in the Folding of Ferrocytochrome C. Biochemistry. 2005 Jul 5;44(26):9359-67. PubMed PMID: 15982002.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Ultrafast events in the folding of ferrocytochrome c. AU - Kumar,Rajesh, AU - Prabhu,N Prakash, AU - Bhuyan,Abani K, PY - 2005/6/29/pubmed PY - 2005/8/27/medline PY - 2005/6/29/entrez SP - 9359 EP - 67 JF - Biochemistry JO - Biochemistry VL - 44 IS - 26 N2 - Laser flash photolysis and stopped-flow methods have been used to study the dynamic events in the micro- to millisecond time bin in the refolding of horse ferrocytochrome c in the full range of guanidine hydrochloride concentration at pH 12.8 (+/-0.1), 22 degrees C. Under the absolute refolding condition, the earliest relaxation time of the unfolded protein chain is less than 1 micros. The chain then undergoes diffusive dynamics-mediated contraction and expansion, in which intrapolypeptide ligands make transient contacts with the heme iron, giving rise to two distinct kinetic phases of approximately 0.4 and approximately 3 micros. Under moderate to absolute refolding conditions, the rates of these processes show little dependence on the denaturant concentration, indicating the absence of structural element in the incipient or the relaxed state. Chain expansion and contraction events continue until the polypeptide finds a stable and supportive transition state. The crossing of this transition barrier, which rate-limits the folding of alkaline ferrocytochrome c, is characterized by a stopped-flow measured time constant of approximately 3 ms in aqueous solvent. Observed kinetics thus implicate no submillisecond folding structure. The folding kinetics is effectively two state in which the unfolded polypeptide first relaxes to an unstructured chain and then crosses over a late rate-limiting barrier to achieve the native conformation. The experimentally observed rates as a function of guanidine hydrochloride concentration have been simulated by numerically calculated microscopic rates of a simple kinetic model that captures the essential features of folding. SN - 0006-2960 UR - https://www.unboundmedicine.com/medline/citation/15982002/Ultrafast_events_in_the_folding_of_ferrocytochrome_c_ DB - PRIME DP - Unbound Medicine ER -
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