Local dynamics and stability of apocytochrome b562 examined by hydrogen exchange

E J Fuentes; A J Wand

doi:10.1021/bi972579s

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Local dynamics and stability of apocytochrome b562 examined by hydrogen exchange

Journal article

Peer reviewed

Local dynamics and stability of apocytochrome b562 examined by hydrogen exchange

E J Fuentes and A J Wand

Biochemistry (Easton), Vol.37(11), pp.3687-3698

03/17/1998

DOI: 10.1021/bi972579s

PMID: 9521687

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Abstract

Cytochrome b562 is a heme-binding protein consisting of four helices folded into a classic helix bundle motif. Though retaining much of the topology of the holoprotein, apocytochrome b562 displays physical features commonly associated with so-called protein molten globules. Here, the stability and dynamics of this "structured" molten globule are probed by examination of the dependence of its hydrogen exchange behavior upon the presence of a chemical denaturant. Compared to other systems studied in this manner, apocytochrome b562 displays a limited dynamic range of hydrogen exchange rates and the analysis required the development of a quantitative approach. The protein is found to have three regions of subglobal cooperative stability. The most stable region, or core, is composed of the central two helices of the bundle, with the N- and C-terminal helices being of independent and lower stability. The dependence of the global unfolding free energy upon denaturant concentration indicates the applicability of a binding model and explains the observed difference between global unfolding free energies obtained by the linear extrapolation method and those obtained by calorimetry and hydrogen exchange. These observations place a significant restraint upon the type of folding pathway that is operative for this protein and suggest that that the N- and C-terminal helices fold and unfold independently of the core of the molecule.

Protons

Amino Acid Sequence

Enzyme Stability

Models, Molecular

Molecular Sequence Data

Guanidine - metabolism

Nitrogen Isotopes

Cytochrome b Group - metabolism

Thermodynamics

Escherichia coli Proteins

Protein Denaturation

Nuclear Magnetic Resonance, Biomolecular

Cytochrome b Group - chemistry

Kinetics

Hydrogen-Ion Concentration

Details

Title: Subtitle: Local dynamics and stability of apocytochrome b562 examined by hydrogen exchange
Creators: E J Fuentes - Department of Chemistry, State University of New York at Buffalo 14260-3000, USA
A J Wand
Resource Type: Journal article
Publication Details: Biochemistry (Easton), Vol.37(11), pp.3687-3698
Publisher: United States
DOI: 10.1021/bi972579s
PMID: 9521687
ISSN: 0006-2960
eISSN: 1520-4995
Grant note: GM 35940 / NIGMS NIH HHS
Language: English
Date published: 03/17/1998
Academic Unit: Biochemistry and Molecular Biology
Record Identifier: 9984025399702771

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