Role of the arginine-45 salt bridge in ligand dissociation from sperm whale carboxymyoglobin as probed by photoacoustic calorimetry

The dynamics of the enthalpy and volume changes found in the photodissociation of CO from sperm whale carboxymyoglobin and two site-directed mutants in which arginine-45 is replaced by glycine and asparagine are examined by photoacoustic calorimetry. An intermediate is observed whose lifetime at 20...

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Bibliographic Details
Published in:Biochemistry (Easton) 1990-07, Vol.29 (28), p.6741-6746
Main Authors: Westrick, Judy A, Peters, Kevin S, Ropp, J. Dezz, Sligar, Stephen G
Format: Article
Language:English
Subjects:
Acoustics
Animals
Arginine
Base Sequence
Calorimetry - methods
Carbon Monoxide - metabolism
Chemical Phenomena
Chemistry, Physical
Diffusion
Molecular Sequence Data
Mutation
Myoglobin - genetics
Myoglobin - metabolism
Myoglobin - radiation effects
Oligodeoxyribonucleotides - chemical synthesis
Photochemistry
Physeter catodon
Protein Engineering
Protons
Recombinant Fusion Proteins - metabolism
Whales
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Summary:The dynamics of the enthalpy and volume changes found in the photodissociation of CO from sperm whale carboxymyoglobin and two site-directed mutants in which arginine-45 is replaced by glycine and asparagine are examined by photoacoustic calorimetry. An intermediate is observed whose lifetime at 20 degrees C is 700 ns. The enthalpy of the intermediate increases by approximately 7 kcal/mol upon replacing arginine-45 with either asparagine or glycine. These observations support recent proposals that an arginine-45 salt bridge is broken upon ligand dissociation.
ISSN:0006-2960
1520-4995
DOI:10.1021/bi00480a026