title: (77)Se enrichment of proteins expands the biological NMR toolbox.
abstract: Sulfur, a key contributor to biological reactivity, is not amendable to investigations by biological NMR spectroscopy. To utilize selenium as a surrogate, we have developed a generally applicable (77)Se isotopic enrichment method for heterologous proteins expressed in Escherichia coli. We demonstrate (77)Se NMR spectroscopy of multiple selenocysteine and selenomethionine residues in the sulfhydryl oxidase augmenter of liver regeneration (ALR). The resonances of the active-site residues were assigned by comparing the NMR spectra of ALR bound to oxidized and reduced flavin adenine dinucleotide. An additional resonance appears only in the presence of the reducing agent and disappears readily upon exposure to air and subsequent reoxidation of the flavin. Hence, (77)Se NMR spectroscopy can be used to report the local electronic environment of reactive and structural sulfur sites, as well as changes taking place in those locations during catalysis.
authors.affiliation: 136 Brown Laboratory, Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA.
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Schaefer
authors.forename: Ming
authors.initials: M
authors.lastname: Dong
authors.forename: Renee P
authors.initials: RP
authors.lastname: Rubenstein
authors.forename: Wayne A
authors.initials: WA
authors.lastname: Wilkie
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Bahnson
authors.forename: Colin
authors.initials: C
authors.lastname: Thorpe
authors.forename: Sharon
authors.initials: S
authors.lastname: Rozovsky
mesh_terms: D002384:Catalysis; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003579:Cytochrome Reductases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005415:Flavins / Q000378:metabolism*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D009154:Mutation / Q000235:genetics; D010084:Oxidation-Reduction; D050862:Oxidoreductases Acting on Sulfur Group Donors; D011487:Protein Conformation; D017510:Protein Folding; D017279:Selenocysteine / Q000378:metabolism*; D012645:Selenomethionine / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D005415:Flavins; D017279:Selenocysteine; D012645:Selenomethionine; D003579:Cytochrome Reductases; C500897:GFER protein, human; D050862:Oxidoreductases Acting on Sulfur Group Donors; D003545:Cysteine