title: Three-dimensional 13C-detected CH3-TOCSY using selectively protonated proteins: facile methyl resonance assignment and protein structure determination.
abstract: Recent advances in instrumentation and isotope labeling methodology allow proteins up to 100 kDa in size to be studied in detail using NMR spectroscopy. Using 2H/13C/15N enrichment and selective methyl protonation, we show that newly developed 13C direct detection methods can be used to rapidly yield proton and carbon resonance assignments for the methyl groups of Val, Leu, and Ile residues. We present a highly sensitive 13C-detected CH3-TOCSY experiment that, in combination with standard 1H-detected backbone experiments, allows the full assignment of side chain resonances in methyl-protonated residues. Selective methyl protonation, originally developed by Kay and co-workers (Rosen, M. K.; Gardner, K. H.; Willis, R. C.; Parris, W. E.; Pawson, T.; Kay, L. E. J. Mol. Biol. 1996, 263, 627-636; Gardner, K. G.; Kay, L. E. Annu. Rev. Biophys. Biomol. Struct. 1998, 27, 357-406; Goto, N. K.; Kay, L. E. Curr. Opin. Struct. Biol. 2000, 10, 585-592), improves the nuclear relaxation behavior of larger proteins compared to their fully protonated counterparts, allows significant simplification of spectra, and facilitates NOE assignments. Here, we demonstrate the usefulness of the 13C-detected CH3-TOCSY experiment through studies of (i) a medium-sized protein (CbpA-R1; 14 kDa) with a repetitive primary sequence that yields highly degenerate NMR spectra, and (ii) a larger, bimolecular protein complex (p21-KID/Cdk2; 45 kDa) at low concentration in a high ionic strength solution. Through the analysis of NOEs involving amide and Ile, Leu, and Val methyl protons, we determined the global fold of CbpA-R1, a bacterial protein that mediates the pathogenic effects of Streptococcus pneumoniae, demonstrating that this approach can significantly reduce the time required to determine protein structures by NMR.
authors.affiliation: Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
authors.forename: John B
authors.initials: JB
authors.lastname: Jordan
authors.forename: Helena
authors.initials: H
authors.lastname: Kovacs
authors.forename: Yuefeng
authors.initials: Y
authors.lastname: Wang
authors.forename: Mehdi
authors.initials: M
authors.lastname: Mobli
authors.forename: Rensheng
authors.initials: R
authors.lastname: Luo
authors.forename: Clemens
authors.initials: C
authors.lastname: Anklin
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Hoch
authors.forename: Richard W
authors.initials: RW
authors.lastname: Kriwacki
mesh_terms: D002244:Carbon / Q000737:chemistry*; D002247:Carbon Isotopes; D051357:Cyclin-Dependent Kinase 2 / Q000737:chemistry*; D019277:Entropy; D006801:Humans; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D011487:Protein Conformation; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry*; D011522:Protons
chemical_list: D002247:Carbon Isotopes; D011522:Protons; D002244:Carbon; D017346:Protein Serine-Threonine Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2