Tuning reduction potentials of type 1 copper center in azurin by replacing a histidine ligand with its isostructural analogues

Yang Yu, Nicholas M. Marshall, Dewain K. Garner, Mark J. Nilges, Yi Lu*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

Type 1 copper proteins have a conserved ligand set of one cysteine and two histidines, with many proteins, such as azurin, also containing an axial methionine. While the cysteine and methionine in azurin have been replaced with their respective isostructural analogues of unnatural amino acids to reveal their roles in tuning electronic structures and functional properties, such as reduction potentials (E°′), the histidine ligands have not been probed in this way. We herein report the substitution of His117 in azurin with three unnatural isostructural analogues, 5-nitrohistidine(Ntr), thiazolylalanine(SHis) and 1-methylhistidine(MeH) by expressed protein ligation. While UV–vis absorption and electron paramagnetic resonance spectroscopies confirm that isostructural replacement results in minimal structural change in the Cu(II) state, the E°′ of these variants increases with increasing pKa of the δ nitrogens of the imidazole. This counter-intuitive relationship between E°′ of the protein and pKa of the sidechain group suggests additional factors may play a role in tuning E°′.

Original languageEnglish
Article number111863
JournalJournal of Inorganic Biochemistry
Volume234
DOIs
Publication statusPublished - Sept 2022
Externally publishedYes

Keywords

  • Blue copper
  • Cupredoxins
  • Electron transfer
  • Protein engineering
  • Redox
  • Unnatural amino acids

Fingerprint

Dive into the research topics of 'Tuning reduction potentials of type 1 copper center in azurin by replacing a histidine ligand with its isostructural analogues'. Together they form a unique fingerprint.

Cite this