Tags

Type your tag names separated by a space and hit enter

Coupled kinetic traps in cytochrome c folding: His-heme misligation and proline isomerization.
J Mol Biol. 2000 May 19; 298(5):955-69.JM

Abstract

The effect of His-heme misligation on folding has been investigated for a triple mutant of yeast iso-2 cytochrome c (N26H,H33N,H39K iso-2). The variant contains a single misligating His residue at position 26, a location at which His residues are found in several cytochrome c homologues, including horse, tuna, and yeast iso-1. The amplitude for fast phase folding exhibits a strong initial pH dependence. For GdnHCl unfolded protein at an initial pH<5, the observed refolding at final pH 6 is dominated by a fast phase (tau(2f)=20 ms, alpha(2f)=90 %) that represents folding in the absence of misligation. For unfolded protein at initial pH 6, folding at final pH 6 occurs in a fast phase of reduced amplitude (alpha(2f) approximately 20 %) but the same rate (tau(2f)=20 ms), and in two slower phases (tau(m)=6-8 seconds, alpha(m) approximately 45 %; and tau(1b)=16-20 seconds, alpha(1b) approximately 35 %). Double jump experiments show that the initial pH dependence of the folding amplitudes results from a slow pH-dependent equilibrium between fast and slow folding species present in the unfolded protein. The slow equilibrium arises from coupling of the His protonation equilibrium to His-heme misligation and proline isomerization. Specifically, Pro25 is predominantly in trans in the unligated low-pH unfolded protein, but is constrained in a non-native cis isomerization state by His26-heme misligation near neutral pH. Refolding from the misligated unfolded form proceeds slowly due to the large energetic barrier required for proline isomerization and displacement of the misligated His26-heme ligand.

Authors+Show Affiliations

Center for Biomolecular Structure, Department of Biochemistry, University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA.No affiliation info available

Pub Type(s)

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

Language

eng

PubMed ID

10801361

Citation

Pierce, M M., and B T. Nall. "Coupled Kinetic Traps in Cytochrome C Folding: His-heme Misligation and Proline Isomerization." Journal of Molecular Biology, vol. 298, no. 5, 2000, pp. 955-69.
Pierce MM, Nall BT. Coupled kinetic traps in cytochrome c folding: His-heme misligation and proline isomerization. J Mol Biol. 2000;298(5):955-69.
Pierce, M. M., & Nall, B. T. (2000). Coupled kinetic traps in cytochrome c folding: His-heme misligation and proline isomerization. Journal of Molecular Biology, 298(5), 955-69.
Pierce MM, Nall BT. Coupled Kinetic Traps in Cytochrome C Folding: His-heme Misligation and Proline Isomerization. J Mol Biol. 2000 May 19;298(5):955-69. PubMed PMID: 10801361.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Coupled kinetic traps in cytochrome c folding: His-heme misligation and proline isomerization. AU - Pierce,M M, AU - Nall,B T, PY - 2000/5/10/pubmed PY - 2000/6/17/medline PY - 2000/5/10/entrez SP - 955 EP - 69 JF - Journal of molecular biology JO - J Mol Biol VL - 298 IS - 5 N2 - The effect of His-heme misligation on folding has been investigated for a triple mutant of yeast iso-2 cytochrome c (N26H,H33N,H39K iso-2). The variant contains a single misligating His residue at position 26, a location at which His residues are found in several cytochrome c homologues, including horse, tuna, and yeast iso-1. The amplitude for fast phase folding exhibits a strong initial pH dependence. For GdnHCl unfolded protein at an initial pH<5, the observed refolding at final pH 6 is dominated by a fast phase (tau(2f)=20 ms, alpha(2f)=90 %) that represents folding in the absence of misligation. For unfolded protein at initial pH 6, folding at final pH 6 occurs in a fast phase of reduced amplitude (alpha(2f) approximately 20 %) but the same rate (tau(2f)=20 ms), and in two slower phases (tau(m)=6-8 seconds, alpha(m) approximately 45 %; and tau(1b)=16-20 seconds, alpha(1b) approximately 35 %). Double jump experiments show that the initial pH dependence of the folding amplitudes results from a slow pH-dependent equilibrium between fast and slow folding species present in the unfolded protein. The slow equilibrium arises from coupling of the His protonation equilibrium to His-heme misligation and proline isomerization. Specifically, Pro25 is predominantly in trans in the unligated low-pH unfolded protein, but is constrained in a non-native cis isomerization state by His26-heme misligation near neutral pH. Refolding from the misligated unfolded form proceeds slowly due to the large energetic barrier required for proline isomerization and displacement of the misligated His26-heme ligand. SN - 0022-2836 UR - https://www.unboundmedicine.com/medline/citation/10801361/Coupled_kinetic_traps_in_cytochrome_c_folding:_His_heme_misligation_and_proline_isomerization_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0022-2836(00)93700-8 DB - PRIME DP - Unbound Medicine ER -