Method and composition for detection of peptide cyclization using protein tags

A method of detecting peptide cyclization comprising

• a) generating a peptide microarray comprising linear peptides coupled to a solid support, wherein each of the linear peptides comprises a variable region and a peptide tag sequence;
• wherein:
• the peptide tag sequence is fragmented across a first end portion and a second end portion of each linear peptide, and
• the variable region is between and does not overlap the first end portion and the second end portion;
• b) cyclizing at least one of the linear peptides to form at least one cyclic peptide coupled to the solid support by combining the first end portion and the second end portion by forming a peptide bond between the first end portion and the second end portion,
• wherein after forming the at least one cyclic peptide, the peptide microarray comprises a mixture of linear and cyclized peptides;
• c) contacting the peptide microarray comprising the at least one cyclic peptide coupled to the solid support with a detectable target protein;
• wherein a binding interaction of the peptide tag sequence with the detectable target protein increases after the cyclizing of the at least one of the linear peptides and the binding interaction has a binding selectivity coefficient of at least 10;
• and
• d) measuring the extent of cyclization by detecting the presence of the detectable target protein that is bound to the peptide tag sequence of the at least one cyclic peptide coupled to the solid support;
• wherein the variable region of the at least one cyclic peptide is capable of binding to a second target protein.