Role of an isoform-specific residue at the calmodulin-heme (NO synthase) interface in the FMN - heme electron transfer

FEBS Lett. 2018 Jul;592(14):2425-2431. doi: 10.1002/1873-3468.13158. Epub 2018 Jun 29.

Abstract

The interface between calmodulin (CaM) and the NO synthase (NOS) heme domain is the least characterized interprotein interface that the NOS isoforms must traverse through during catalysis. Our previous molecular dynamics simulations predicted a salt bridge between K497 in human inducible NOS (iNOS) heme domain and D118(CaM). Herein, the FMN - heme interdomain electron transfer (IET) rate was found to be notably decreased by charge-reversal mutation, while the IET in the iNOS K497D mutant is significantly restored by the CaM D118K mutation. The results of wild-type protein with added synthetic peptides further demonstrate the critical nature of K497 relative to the rest of the peptide sequence in modulating the IET. These data provide definitive evidence supporting the regulatory role of the isoform-specific K497 residue.

Keywords: calmodulin; heme-FMN electron transfer; nitric oxide synthase.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amino Acid Sequence
  • Amino Acid Substitution / genetics
  • Calmodulin / chemistry
  • Calmodulin / genetics
  • Calmodulin / metabolism*
  • Codon, Nonsense
  • Electron Transport / physiology
  • Flavin Mononucleotide / metabolism*
  • Heme / chemistry
  • Heme / metabolism*
  • Humans
  • Models, Molecular
  • Molecular Dynamics Simulation
  • Mutagenesis, Site-Directed
  • Nitric Oxide Synthase Type II / chemistry*
  • Nitric Oxide Synthase Type II / genetics
  • Nitric Oxide Synthase Type II / metabolism*
  • Oxidation-Reduction
  • Protein Interaction Domains and Motifs / genetics
  • Protein Interaction Domains and Motifs / physiology*
  • Protein Isoforms / genetics
  • Protein Isoforms / physiology
  • Protein Structure, Secondary

Substances

  • Calmodulin
  • Codon, Nonsense
  • Protein Isoforms
  • Heme
  • Flavin Mononucleotide
  • NOS2 protein, human
  • Nitric Oxide Synthase Type II