Specific electrochemical iodination of horse heart myoglobin at tyrosine 103 as determined by Fourier transform ion cyclotron resonance mass spectrometry.
The iodination of proteins remains a useful tool in biochemistry for radiolabelling. However, chemical or enzymatic iodination is difficult to control and can give deleterious polyiodination. Previously, we have shown that electrooxidation with nitrite is a rapid method for the selective nitration of tyrosine residues in proteins. In principle, it should be possible to substitute a number of electrooxidisable anions into the tyrosine phenol ring. Electrochemical iodination is more difficult to control than nitration because the rapid anodic oxidation of I(-) leads to persistent formation of the iodinating triiodide anion. However, application of pulsed electrooxidation and reduction cycles is shown to be an effective procedure for the selective mono and double-iodination of myoglobin, which may have general application to other proteins in controlling of the level of iodination. Mono- and double-iodination of myoglobin by this method was confirmed by electrospray FT-ICR mass spectrometry. Infrared multiphoton dissociation (IRMPD) enabled localization of the site of mono-iodination to be restricted to either His97 or Tyr103. More extensive sequence coverage was obtained with electron capture dissociation (ECD), allowing unambiguous assignment of the site of iodination to Tyr103.
Iniesta
Jesus
J
Centre for Molecular and Biomedical Science, Faculty of Health and Life Sciences, Coventry University, Coventry CV1 5FB, UK.
Cooper
Helen J
HJ
Marshall
Alan G
AG
Heptinstall
John
J
Walton
David J
DJ
Peterson
Ian R
IR
D000818:Animals; D017357:Cyclotrons; D004563:Electrochemistry / Q000379:methods*; D006736:Horses; D013058:Mass Spectrometry / Q000379:methods*; D009211:Myoglobin / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D014443:Tyrosine / Q000737:chemistry*
D009211:Myoglobin; D014443:Tyrosine