title: The best and the brightest: exploiting tryptophan-sensitized Tb(3+) luminescence to engineer lanthanide-binding tags.
abstract: Consider the lanthanide metals, comprising lanthanum through lutetium. Lanthanides form stable cations with a +3 charge, and these ions exhibit a variety of useful physical properties (long-lifetime luminescence, paramagnetism, anomalous X-ray scattering) that are amenable to studies of biomolecules. The absence of lanthanide ions in living systems means that background signals are generally a nonissue; however, to exploit the advantageous properties it is necessary to engineer a robust lanthanide-binding sequence that can be appended to any macromolecules of interest. To this end, the luminescence produced by tryptophan-sensitized Tb(3+) has been used as a selection marker for peptide sequences that avidly chelate these ions. A combinatorial split-and-pool library that uses two orthogonal linkers-one that is cleaved for selection and one that is cleaved for sequencing and characterization-has been used to develop lanthanide-binding tags (LBTs): peptides of 15-20 amino acids with low-nM affinity for Tb(3+). Further validating the success of this screen, knowledge about LBTs has enabled the introduction of a lanthanide-binding loop in place of one of the four native calcium-binding loops within the protein calcineurin B.
authors.affiliation: Department of Chemistry and Physics, Warren Wilson College, Asheville, NC, USA.
authors.forename: Langdon J
authors.initials: LJ
authors.lastname: Martin
authors.forename: Barbara
authors.initials: B
authors.lastname: Imperiali
mesh_terms: D000818:Animals; D019703:Calcineurin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008164:Luminescent Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D019151:Peptide Library; D011485:Protein Binding; D015202:Protein Engineering / Q000379:methods*; D017433:Protein Structure, Secondary; D013725:Terbium / Q000737:chemistry*; D014364:Tryptophan / Q000737:chemistry / Q000378:metabolism
chemical_list: D008164:Luminescent Proteins; D019151:Peptide Library; D013725:Terbium; D014364:Tryptophan; D019703:Calcineurin; D002118:Calcium