Structural and thermodynamic encoding in the sequence of rat microsomal cytochrome b5†

  1. Juliette T. J. Lecomte‡*,
  2. Kunal Mukhopadhyay§,
  3. Matthew P. Pond‡

Article first published online: 26 NOV 2007

DOI: 10.1002/bip.20892

Issue

Biopolymers

Biopolymers

Special Issue: This issue is dedicated to the memory of Elkan R. Blout, a founding editor of Biopolymers

Volume 89, Issue 5, pages 428–442, May 2008

Additional Information

How to Cite

Lecomte, J. T. J., Mukhopadhyay, K. and Pond, M. P. (2008), Structural and thermodynamic encoding in the sequence of rat microsomal cytochrome b5. Biopolymers, 89: 428–442. doi: 10.1002/bip.20892

Author Information

  1. Department of Chemistry, The Pennsylvania State University, University Park, PA 16802

  1. §

    Bio-Rad Laboratories AB, Sundbyberg, Sweden

  2. ‡

    Department of Biophysics, Johns Hopkins University, Baltimore, MD 21218

*Department of Chemistry, The Pennsylvania State University, University Park, PA 16802

  1. †

    This article concerns a protein folding problem formulated many years ago by Professor Blout. His insights into the conformational properties of peptides and proteins in their native and unfolded states and the potential for certain sequences to undergo coupled binding and refolding set the stage for modern folding studies.

Publication History

  1. Issue published online: 28 FEB 2008
  2. Article first published online: 26 NOV 2007
  3. Manuscript Accepted: 5 NOV 2007
  4. Manuscript Received: 3 OCT 2007

Funded by

  • National Institutes of Health. Grant Number: GM-54217

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Keywords:

  • apoprotein;
  • intrinsically unfolded protein;
  • heme;
  • induced refolding

Abstract

The water-soluble domain of rat microsomal cytochrome b5 is a convenient protein with which to inspect the connection between amino acid sequence and thermodynamic properties. In the absence of its single heme cofactor, cytochrome b5 contains a partially folded stretch of ˜30 residues. This region is recognized as prone to disorder by programs that analyze primary structures for such intrinsic features. The cytochrome was subjected to amino acid replacements in the folded core (I12A), in the portion that refolds only when in contact with the heme group (N57P), and in both (F35H/H39A/L46Y). Despite the difficulties associated with measuring thermodynamic quantities for the heme-bound species, it was possible to rationalize the energetic consequences of both types of replacements and test a simple equation relating apoprotein and holoprotein stability. In addition, a phenomenological relationship between the change in Tm (the temperature at the midpoint of the thermal transition) and the change in thermodynamic stability determined by chemical denaturation was observed that could be used to extend the interpretation of incomplete holoprotein stability data. Structural information was obtained by nuclear magnetic resonance spectroscopy toward an atomic-level analysis of the effects. © 2007 Wiley Periodicals, Inc. Biopolymers 89: 428–442, 2008.

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com

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