The formation of a fluorescent protein chromophore cross-link from the alpha-carboxyl carbon of residue n, a lysine, to the alpha-amino nitrogen of residue n+2, a glycine, and a dehydration to form a double bond to the alpha-amino nitrogen of residue n+1. This cross-linking is coupled with a dehydrogenation of residue n+1 to form a double bond between the alpha and beta carbons.