Fast events in protein folding

Relaxation dynamics and structure of the I form of apomyoglobin

Rudolf Gilmanshin, Skip Williams, Robert Callender, William H. Woodruff, R. Brian Dyer

Research output: Contribution to journalArticle

64 Citations (Scopus)

Abstract

The fast relaxation dynamics of the acid destabilized I form of apomyoglobin (pH* 3, 0.15 M NaCl; apoMb-I) following a laser-induced temperature-jump have been probed using time-resolved infrared spectroscopy. Only a fast, single exponential phase is observed (bleach centered at v = 1633 cm-1 and transient absorbance at 1666 cm-1) with relaxation times of 38 ns at 30 °C and 36 ns at 57 °C; no additional slow (microsecond) phase is observed as previously found in the native form of apomyoglobin. Folding times of approximately 66 ns are derived from the observed rates based on a simple two-state model. The equilibrium melting of the 1633 cm-1 component shows noncooperative linear behavior over the temperature range studied (10- 60 °C). The low amide I' frequency, the fast relaxation dynamics, and the noncooperative melting behavior are characteristic of isolated solvated helix. The analysis of the amide-I' band reveals another major component at 1650 cm-1 assigned to native-like structure stabilized by tertiary contacts involving the AGH core, which does not show dynamic or static melting under our conditions. ApoMb-I has generally been taken to be a 'molten globule' species. The present results indicate a heterogeneous structure consisting of separate regions of native-like unit(s), solvated helices, and disordered coil, excluding a homogeneous molten globule as a model for apoMb-I. From the current studies and other results, a detailed model of the folding of apomyoglobin is presented.

Original languageEnglish (US)
Pages (from-to)15006-15012
Number of pages7
JournalBiochemistry
Volume36
Issue number48
DOIs
StatePublished - Dec 2 1997

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Protein folding
Protein Folding
Freezing
Melting
Amides
Molten materials
Temperature
Relaxation time
Infrared spectroscopy
Spectrum Analysis
Lasers
Acids
apomyoglobin

ASJC Scopus subject areas

  • Biochemistry

Cite this

Fast events in protein folding : Relaxation dynamics and structure of the I form of apomyoglobin. / Gilmanshin, Rudolf; Williams, Skip; Callender, Robert; Woodruff, William H.; Dyer, R. Brian.

In: Biochemistry, Vol. 36, No. 48, 02.12.1997, p. 15006-15012.

Research output: Contribution to journalArticle

Gilmanshin, Rudolf ; Williams, Skip ; Callender, Robert ; Woodruff, William H. ; Dyer, R. Brian. / Fast events in protein folding : Relaxation dynamics and structure of the I form of apomyoglobin. In: Biochemistry. 1997 ; Vol. 36, No. 48. pp. 15006-15012.
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