Identification of cyclized calmodulin antagonists from a phage display random peptide library |
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Authors: | Heather Hanson Pierce Nils Adey Brian K. Kay |
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Affiliation: | (1) Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, 27599 Chapel Hill, NC, USA;(2) Department of Biology, University of North Carolina at Chapel Hill, 27599 Chapel Hill, NC, USA;(3) Myriad Genetics, 84108 Salt Lake City, UT, USA |
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Abstract: | Summary To isolate peptide ligands that bound calmodulin (CaM) specifically, we screened an M13 phage library displaying cyclized octamer random peptides with immobilized bovine CaM. Isolates were recovered, sequenced, and deduced to express nine independent peptides, five of which contained the sequence Trp-Gly-Lys (WGK). Four of the nine peptide sequences were synthesized in cyclized, biotinylated form. All of the peptides required Ca2+ to bind CaM. The cyclized, disulfide-bonded form of one such peptide, SCLRWGKWSNCGS, bound CaM better than its reduced form or an analogue in which the cysteine residues were replaced by serine. The cyclized peptide also exhibited the ability to inhibit CaM-dependent kinase activity. Systematic alanine substitution of residues in this peptide sequence implicate the tryptophan residue as being critical for binding, with other residues contributing to binding to varying degrees. Cloning of ligand targets (COLT) confirmed the specificity of one of the cyclized peptides, yielding full-length and C-terminal CaM clones, in addition to a full-length clone of troponin C, a CaM-related protein. This study has demonstrated that conformationally constrained peptides isolated from a phage library acted as specific, Ca2+-dependent CaM ligands. |
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Keywords: | Bacteriophage M13 Phage display Conformationally constrained peptides Calmodulin Antagonists Mutagenesis Alanine-scanning |
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