A Caltech Library Service

Copper-sulfenate complex from oxidation of a cavity mutant of Pseudomonas aeruginosa azurin

Sieracki, Nathan A. and Tian, Shiliang and Hadt, Ryan G. and Zhang, Jun-Long and Woertink, Julia S. and Nilges, Mark J. and Sun, Furong and Solomon, Edward I. and Lu, Yi (2014) Copper-sulfenate complex from oxidation of a cavity mutant of Pseudomonas aeruginosa azurin. Proceedings of the National Academy of Sciences of the United States of America, 111 (3). pp. 924-929. ISSN 0027-8424. PMCID PMC3903256. doi:10.1073/pnas.1316483111.

[img] PDF - Published Version
See Usage Policy.

[img] PDF - Supplemental Material
See Usage Policy.


Use this Persistent URL to link to this item:


Metal-sulfenate centers are known to play important roles in biology and yet only limited examples are known due to their instability and high reactivity. Herein we report a copper-sulfenate complex characterized in a protein environment, formed at the active site of a cavity mutant of an electron transfer protein, type 1 blue copper azurin. Reaction of hydrogen peroxide with Cu(I)-M121G azurin resulted in a species with strong visible absorptions at 350 and 452 nm and a relatively low electron paramagnetic resonance gz value of 2.169 in comparison with other normal type 2 copper centers. The presence of a side-on copper-sulfenate species is supported by resonance Raman spectroscopy, electrospray mass spectrometry using isotopically enriched hydrogen peroxide, and density functional theory calculations correlated to the experimental data. In contrast, the reaction with Cu(II)-M121G or Zn(II)-M121G azurin under the same conditions did not result in Cys oxidation or copper-sulfenate formation. Structural and computational studies strongly suggest that the secondary coordination sphere noncovalent interactions are critical in stabilizing this highly reactive species, which can further react with oxygen to form a sulfinate and then a sulfonate species, as demonstrated by mass spectrometry. Engineering the electron transfer protein azurin into an active copper enzyme that forms a copper-sulfenate center and demonstrating the importance of noncovalent secondary sphere interactions in stabilizing it constitute important contributions toward the understanding of metal-sulfenate species in biological systems.

Item Type:Article
Related URLs:
URLURL TypeDescription CentralArticle Information
Hadt, Ryan G.0000-0001-6026-1358
Solomon, Edward I.0000-0003-0291-3199
Lu, Yi0000-0003-1221-6709
Additional Information:© 2014 National Academy of Sciences. Edited by Harry B. Gray, California Institute of Technology, Pasadena, CA, and approved November 27, 2013 (received for review September 3, 2013) We thank Drs. Peter M. Yau and Brian S. Imai from the Protein Science Facility in the Biotechnology Center at the University of Illinois at Urbana–Champaign for performing trypsin digest and HPLC MS/MS analysis of the protein. Use of the Advanced Photon Source, an Office of Science User Facility operated for the US Department of Energy (DOE) Office of Science by Argonne National Laboratory, was supported by the US DOE under Contract DE-AC02-06CH11357. Use of the life science collaborative access team (LS-CAT) Sector 21 was supported by the Michigan Economic Development Corporation and the Michigan Technology Tri-Corridor (Grant 085P1000817). This work is based on work supported by the National Science Foundation under Awards CHE 1058959 (to Y.L.) and CHE 0948211 (to E.I.S.). R.G.H. acknowledges a Gerhard Casper Stanford Graduate Fellowship and the Achievement Rewards for College Scientists (ARCS) Foundation. N.A.S., S.T., and R.G.H. contributed equally to this work. Author contributions: N.A.S., S.T., J.-L.Z., and Y.L. designed research; N.A.S., S.T., R.G.H., J.-L.Z., and J.S.W. performed research; N.A.S., S.T., R.G.H., J.-L.Z., M.J.N., F.S., E.I.S., and Y.L. analyzed data; and N.A.S., S.T., R.G.H., E.I.S., and Y.L. wrote the paper. The authors declare no conflict of interest. This article is a PNAS Direct Submission. Data deposition: The atomic coordinates and structures factors have been deposited in the Protein Data Bank, (PDB ID codes 4MFH and 4AZU). This article contains supporting information online at
Funding AgencyGrant Number
Department of Energy (DOE)DE-AC02-06CH11357
Michigan Economic Development CorporationUNSPECIFIED
Michigan Technology Tri-Corridor085P1000817
Stanford UniversityUNSPECIFIED
Subject Keywords:bioinorganic chemistry; blue copper proteins; metalloprotein design; posttranslational modification; protein engineering
Issue or Number:3
PubMed Central ID:PMC3903256
Record Number:CaltechAUTHORS:20180612-114523845
Persistent URL:
Official Citation:Copper–sulfenate complex from oxidation of a cavity mutant of Pseudomonas aeruginosa azurin. Nathan A. Sieracki, Shiliang Tian, Ryan G. Hadt, Jun-Long Zhang, Julia S. Woertink, Mark J. Nilges, Furong Sun, Edward I. Solomon, Yi Lu. Proceedings of the National Academy of Sciences Jan 2014, 111 (3) 924-929; DOI: 10.1073/pnas.1316483111
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:87008
Deposited By: George Porter
Deposited On:12 Jun 2018 20:11
Last Modified:15 Nov 2021 20:44

Repository Staff Only: item control page