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Energetic frustration of apomyoglobin folding: role of the B helix.
J Mol Biol. 2010 Mar 12; 396(5):1319-28.JM

Abstract

Apomyoglobin folds by a sequential mechanism in which the A, G, and H helix regions undergo rapid collapse to form a compact intermediate onto which the central portion of the B helix subsequently docks. To investigate the factors that frustrate folding, we have made mutations in the N-terminus of the B helix to stabilize helical structure (in the mutant G23A/G25A) and to promote native-like hydrophobic packing interactions with helix G (in the mutant H24L/H119F). The kinetic and equilibrium intermediates of G23A/G25A and H24L/H119F were studied by hydrogen exchange pulse labeling and interrupted hydrogen/deuterium exchange combined with NMR. For both mutants, stabilization of helical structure in the N-terminal region of the B helix is confirmed by increased exchange protection in the equilibrium molten globule states near pH 4. Increased protection is also observed in the GH turn region in the G23A/G25A mutant, suggesting that stabilization of the B helix facilitates native-like interactions with the C-terminal region of helix G. These interactions are further enhanced in H24L/H119F. The kinetic burst phase intermediates of both mutants show increased protection, relative to wild-type protein, of amides in the N-terminus of the B helix and in part of the E helix. Stabilization of the E helix in the intermediate is attributed to direct interactions between E helix residues and the newly stabilized N-terminus of helix B. Stabilization of native packing between the B and G helices in H24L/H119F also favors formation of native-like interactions in the GH turn and between the G and H helices in the ensemble of burst phase intermediates. We conclude that instability at the N-terminus of the B helix of apomyoglobin contributes to the energetic frustration of folding by preventing docking and stabilization of the E helix.

Authors+Show Affiliations

Department of Molecular Biology and Skaggs Institute of Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural

Language

eng

PubMed ID

20043917

Citation

Nishimura, Chiaki, et al. "Energetic Frustration of Apomyoglobin Folding: Role of the B Helix." Journal of Molecular Biology, vol. 396, no. 5, 2010, pp. 1319-28.
Nishimura C, Dyson HJ, Wright PE. Energetic frustration of apomyoglobin folding: role of the B helix. J Mol Biol. 2010;396(5):1319-28.
Nishimura, C., Dyson, H. J., & Wright, P. E. (2010). Energetic frustration of apomyoglobin folding: role of the B helix. Journal of Molecular Biology, 396(5), 1319-28. https://doi.org/10.1016/j.jmb.2009.12.040
Nishimura C, Dyson HJ, Wright PE. Energetic Frustration of Apomyoglobin Folding: Role of the B Helix. J Mol Biol. 2010 Mar 12;396(5):1319-28. PubMed PMID: 20043917.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Energetic frustration of apomyoglobin folding: role of the B helix. AU - Nishimura,Chiaki, AU - Dyson,H Jane, AU - Wright,Peter E, Y1 - 2010/01/04/ PY - 2009/10/16/received PY - 2009/12/15/revised PY - 2009/12/18/accepted PY - 2010/1/2/entrez PY - 2010/1/2/pubmed PY - 2010/3/23/medline SP - 1319 EP - 28 JF - Journal of molecular biology JO - J Mol Biol VL - 396 IS - 5 N2 - Apomyoglobin folds by a sequential mechanism in which the A, G, and H helix regions undergo rapid collapse to form a compact intermediate onto which the central portion of the B helix subsequently docks. To investigate the factors that frustrate folding, we have made mutations in the N-terminus of the B helix to stabilize helical structure (in the mutant G23A/G25A) and to promote native-like hydrophobic packing interactions with helix G (in the mutant H24L/H119F). The kinetic and equilibrium intermediates of G23A/G25A and H24L/H119F were studied by hydrogen exchange pulse labeling and interrupted hydrogen/deuterium exchange combined with NMR. For both mutants, stabilization of helical structure in the N-terminal region of the B helix is confirmed by increased exchange protection in the equilibrium molten globule states near pH 4. Increased protection is also observed in the GH turn region in the G23A/G25A mutant, suggesting that stabilization of the B helix facilitates native-like interactions with the C-terminal region of helix G. These interactions are further enhanced in H24L/H119F. The kinetic burst phase intermediates of both mutants show increased protection, relative to wild-type protein, of amides in the N-terminus of the B helix and in part of the E helix. Stabilization of the E helix in the intermediate is attributed to direct interactions between E helix residues and the newly stabilized N-terminus of helix B. Stabilization of native packing between the B and G helices in H24L/H119F also favors formation of native-like interactions in the GH turn and between the G and H helices in the ensemble of burst phase intermediates. We conclude that instability at the N-terminus of the B helix of apomyoglobin contributes to the energetic frustration of folding by preventing docking and stabilization of the E helix. SN - 1089-8638 UR - https://www.unboundmedicine.com/medline/citation/20043917/Energetic_frustration_of_apomyoglobin_folding:_role_of_the_B_helix_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0022-2836(09)01547-2 DB - PRIME DP - Unbound Medicine ER -