an S-sulfanyl-[ThiI sulfur-carrier protein] + a carboxy-adenylated-[ThiS sulfur-carrier protein] + 2 a reduced ferredoxin [iron-sulfur] cluster → a thiocarboxy-[ThiS-Protein] + a ThiI sulfur-carrier protein + AMP + 2 an oxidized ferredoxin [iron-sulfur] cluster