Design of affinity peptides from natural protein ligands: A study of the cardiac troponin complex

Development of a fluorescent cardiomyocyte specific binding probe

Cardiomyocytes are the major component of the heart. Their dysfunction or damage could lead to serious cardiovascular diseases, which have claimed numerous lives around the world. A molecule able to recognize cardiomyocytes would have significant value in diagnosis and treatment. Recently a novel peptide termed myocyte targeting peptide (MTP), with three residues of a non-natural amino acid biphenylalanine (Bip), showed good affinity to cardiomyocytes. Its selectivity towards cardiac tissues was concluded to be due to the ability of Bip to bind cardiac troponin I. With the aim of optimizing the affinity and the specificity towards cardiac myocytes and to better understand structure-activity relationship, a library of MTP derivatives was designed. Exploiting a fluorescent tag, the selectivity of the MTP analogs to myocardium over skeletal and stomach muscle tissues was assayed by fluorescence imaging. Among the tested sequences, the peptide probe Bip2, H-Lys(FITC)-Arg-Arg-Arg-Arg-Arg-Arg-Arg-Gly-Ser-Gly-Ser-Bip-Bip-NH2, displayed the best selectivity for cardiomyocytes.