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Structural and thermodynamic encoding in the sequence of rat microsomal cytochrome b 5
Author(s) -
Lecomte Juliette T. J.,
Mukhopadhyay Kunal,
Pond Matthew P.
Publication year - 2008
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.20892
Subject(s) - chemistry , heme , cytochrome , chemical stability , crystallography , preprint , denaturation (fissile materials) , thermodynamics , cytochrome c , sequence (biology) , stereochemistry , biochemistry , organic chemistry , physics , mitochondrion , nuclear chemistry , enzyme , world wide web , computer science
The water‐soluble domain of rat microsomal cytochrome b 5 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 b 5 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 T m (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