Proton NMR studies of myohemerythrin from Themiste zostericola

Zhigang Wang, Laura Martins, Walther R. Ellis, Lawrence Que

Research output: Contribution to journalArticle

Abstract

One- and two-dimensional NMR experiments have been carried out on different forms of myohemerythrin (MHr), a monomeric 13.9-kDa oxygen carrier, focusing on paramagnetically shifted proton resonances. Compared to the corresponding forms of octameric hemerythrin (Hr), all of the MHr forms exhibit spectra with better resolution and signal-to-noise ratios. The metMHr spectra allow the differentiation of the signals from the N(δ)-H protons of the five N(r)-coordinated His ligands and those from the bridging Asp and Glu ligands. The ID spectra of deoxyMHr exhibit a number of relatively sharp features including three solvent-exchangeable peaks that account for five protons. One of these His N-H protons exchanges more slowly with solvent than the other four and is assigned to His 54, which, by analogy to the crystal structure of deoxy-Hr, is the only His ligand that is hydrogen-bonded to an amine acid residue, Glu24 in this case. One-dimensional NOE results on the non-exchangeable signals clearly show the connectivities among the α and β protons of the bridging Asp111, and the α,β, and γ protons of the bridging Glu58 ligands. One-dimensional NOE experiments performed on the N-H proton signals of the coordinated His ligands, together with the COSY results, help to identify the geminal β protons of the His ligands. Upon the binding of N3/- to one of the Fe(II) sites in deoxyMHr, the overlapping His N(δ)-H protonsignals observed in the deoxyMHr spectrum are resolved into individual signals; these have been correlated to the corresponding signals in deoxyMHr by saturation transfer experiments. Similarly, all five His N-H protons are resolved in the 1H NMR spectrum of the deoxy form of the single point mutant L103N MHr. However, all five N-H protons readily exchange with solvent, indicating that the mutation affects the hydrogen-bonding interaction between His54 and Glu24.

Original languageEnglish (US)
Pages (from-to)56-64
Number of pages9
JournalJournal of Biological Inorganic Chemistry
Volume2
Issue number1
DOIs
StatePublished - Feb 1 1997
Externally publishedYes

Keywords

  • Myohemerythrin
  • Nuclear magnetic resonance
  • Solvent-exchangeable protons
  • Themiste zostericola

ASJC Scopus subject areas

  • Biochemistry
  • Inorganic Chemistry

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