Role of ArCP in yersiniabactin synthesis. a) ArCP is the first carrier protein domain of
HMWP2, which also comprises two cyclization domains (Cy1 and Cy2), two peptidyl carrier
proteins (PCP1 and PCP2), an adenylation domain for cysteine (A), and an epimerization
domain embedded in the A-domain (E). b) The A-domain loads cysteine onto PCP1 and PCP2,
and the stand alone A-domain YbtE loads salicylate onto ArCP. c) Cy1 catalyzes the
condensation and cyclodehydration of Sal and Cys, forming 2-hydroxyphenylthiazoline on
PCP1 and returning ArCP to its holo form. Not shown: Cy2, HMWP1 (a mixed PKS NRPS
protein), and YbtU complete the synthesis of yersiniabactin (e). d) Nomenclature used to
assign phosphopantetheine (J-U) and salicylate
(V-AA) is shown in italics.