title: A dipicolinic acid tag for rigid lanthanide tagging of proteins and paramagnetic NMR spectroscopy.
abstract: A new lanthanide tag was designed for site-specific labeling of proteins with paramagnetic lanthanide ions. The tag, 4-mercaptomethyl-dipicolinic acid, binds lanthanide ions with nanomolar affinity, is readily attached to proteins via a disulfide bond, and avoids the problems of diastereomer formation associated with most of the conventional lanthanide tags. The high lanthanide affinity of the tag opens the possibility to measure residual dipolar couplings in a single sample containing a mixture of paramagnetic and diamagnetic lanthanides. Using the DNA-binding domain of the E. coli arginine repressor as an example, it is demonstrated that the tag allows immobilization of the lanthanide ion in close proximity of the protein by additional coordination of the lanthanide by a carboxyl group of the protein. The close proximity of the lanthanide ion promotes accurate determinations of magnetic susceptibility anisotropy tensors. In addition, the small size of the tag makes it highly suitable for studies of intermolecular interactions.
authors.affiliation: Research School of Chemistry, Australian National University, Canberra ACT 0200, Australia.
authors.forename: Xun-Cheng
authors.initials: XC
authors.lastname: Su
authors.forename: Bradley
authors.initials: B
authors.lastname: Man
authors.forename: Sophie
authors.initials: S
authors.lastname: Beeren
authors.forename: Haobo
authors.initials: H
authors.lastname: Liang
authors.forename: Shane
authors.initials: S
authors.lastname: Simonsen
authors.forename: Christophe
authors.initials: C
authors.lastname: Schmitz
authors.forename: Thomas
authors.initials: T
authors.lastname: Huber
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Messerle
authors.forename: Gottfried
authors.initials: G
authors.lastname: Otting
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry; D029968:Escherichia coli Proteins / Q000737:chemistry; D028581:Lanthanoid Series Elements / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular; D010848:Picolinic Acids / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry*; D012097:Repressor Proteins / Q000737:chemistry; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: C531914:4-mercaptomethyldipicolinic acid; C087018:ArgR protein, Bacteria; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D028581:Lanthanoid Series Elements; D010848:Picolinic Acids; D011506:Proteins; D012097:Repressor Proteins; D013438:Sulfhydryl Compounds