Role of the Arginine-45 Salt Bridge in Ligand Dissociation from Sperm Whale Carboxymyoglobin As Probed by Photoacoustic Calorimetry

Judy A. Westrick, Kevin S. Peters, J. Dezz Ropp, Stephen G. Sligar

Research output: Contribution to journalArticlepeer-review

Abstract

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°C is 700 ns. The enthalpy of the intermediate increases by ~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.

Original languageEnglish (US)
Pages (from-to)6741-6746
Number of pages6
JournalBiochemistry
Volume29
Issue number28
DOIs
StatePublished - Jan 7 1990

ASJC Scopus subject areas

  • Biochemistry

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