NMR studies of oxyleghemoglobin. Assignment of distal histidine proton resonances and evidence for pH-dependent changes in conformation

Bridget C. Mabbutt, Cyril A. Appleby, Peter E. Wright*

*Corresponding author for this work

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

The resonance of the C-2 proton of the distal histidine has been assigned in the 400 MHz 1H-NMR spectrum of soybean oxyleghemoglobin a. This resonance is subject to a very large ring current shift from the heme and occurs to high field of the residual HO2H peak. The pH dependence was measured from a series of nuclear Overhauser effect difference spectra over a range of pH values. The resonance moves to high field with decreasing pH and reflects titration of a one proton-dissociable group with pK 5.5. Resonances of the heme substituents and distal amino acid side-chains are also sensitive to this titration. Changes in ring-current shifts and nuclear Overhauser effects indicate that a conformational change occurs in the heme pocket upon titration of the pK 5.5 group. We propose that protonation of the distal histidine with pK 5.5 is accompanied by movement of the imidazole ring towards the heme normal. This movement would allow interaction between the ligated oxygen molecule and the protonated distal histidine at acid pH.

Original languageEnglish
Pages (from-to)281-288
Number of pages8
JournalBiochimica et Biophysica Acta (BBA)/Protein Structure and Molecular
Volume749
Issue number3
DOIs
Publication statusPublished - 28 Dec 1983
Externally publishedYes

Keywords

  • (Soybean)
  • H-NMR
  • Distal histidine
  • Histidine
  • Oxygen binding
  • Oxyleghemoglobin

Fingerprint Dive into the research topics of 'NMR studies of oxyleghemoglobin. Assignment of distal histidine proton resonances and evidence for pH-dependent changes in conformation'. Together they form a unique fingerprint.

  • Cite this