Proton nuclear overhauser effect investigation of the heme pocket expansion in trimethyl phosphine sperm whale myoglobin

Abstract

Abstract Two-dimensional nuclear magnetic resonance spectroscopy (2D NMR) was used to assign amino acid residues from the distal side of the heme pocket in the 1 H-NMR spectrum of trimethyl phosphine sperm whale myoglobin. The unambiguous assignment of the heme substituents and NOE connectivities from the resonances of trimethyl phosphine protons formed the basis for the identification of amino acid residues. Our results suggest assignment of the aromatic resonances corresponding to Phe-33 (B 14 ), Phe-43 (CD 1 ), Phe-46 (CD 4 ) and His-64 (E 7 ). These assignments provide comparative information on the conformation of the heme pocket in complexes of sperm whale myoglobin with two different ligands CO and PMe 3 . The difference in the spatial disposition of the Val-68 side-chain and the Phe-43 and His-64 rings between the two complexes confirms the greater steric hindrance in MbPMe 3 .