HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Schwarzinger, S. Articles by Wright, P. E. Search for Related Content PubMed PubMed Citation Articles by Schwarzinger, S. Articles by Wright, P. E. Social Bookmarking                   What's this?

Structural characterization of partially folded intermediates of apomyoglobin H64F

¹ Department of Molecular Biology, The Scripps Research Institute and Skaggs Institute for Chemical Biology, La Jolla, California 92037, USA

(RECEIVED September 5, 2007; FINAL REVISION October 12, 2007; ACCEPTED October 16, 2007)

We present a detailed investigation of unfolded and partially folded states of a mutant apomyoglobin (apoMb) where the distal histidine has been replaced by phenylalanine (H64F). Previous studies have shown that substitution of His64, located in the E helix of the native protein, stabilizes the equilibrium molten globule and native states and leads to an increase in folding rate and a change in the folding pathway. Analysis of changes in chemical shift and in backbone flexibility, detected via [¹H]-¹⁵N heteronuclear nuclear Overhauser effect measurements, indicates that the phenylalanine substitution has only minor effects on the conformational ensemble in the acid- and urea-unfolded states, but has a substantial effect on the structure, dynamics, and stability of the equilibrium molten globule intermediate formed near pH 4. In H64F apomyoglobin, additional regions of the polypeptide chain are recruited into the compact core of the molten globule. Since the phenylalanine substitution has negligible effect on the unfolded ensemble, its influence on folding rate and stability comes entirely from interactions within the compact folded or partly folded states. Replacement of His64 with Phe leads to favorable hydrophobic packing between the helix E region and the molten globule core and leads to stabilization of helix E secondary structure and overall thermodynamic stabilization of the molten globule. The secondary structure of the equilibrium molten globule parallels that of the burst phase kinetic intermediate; both intermediates contain significant helical structure in regions of the polypeptide that comprise the A, B, E, G, and H helices of the fully folded protein.

Keywords: protein folding; protein stability; hydrophobic interaction; chain dynamics; NMR spectroscopy; myoglobin; molten globule

CiteULike

Connotea

Del.icio.us

Digg

Reddit

Technorati