Catechol conjugation with hemolymph proteins and their incorporation into the cuticle of the American cockroach, Periplaneta americana

Newly ecdysed American cockroaches, Periplaneta americana (sixth to last in star) were injected with radioactive dopamine (DA) and hemolymph was collec ted at 10-60 min post-ecdysis. Size-exclusion chromatography established th e presence of at least three proteins that serve as catecholamine carriers. Reinjection of the smaller radiolabeled phenol-bound proteins into newly e cdysed animals results in in vivo aggregation, with the radiolabel bound to large MW proteins (30- > 200 kDa). In addition, the reinjection of radiola beled protein of any size resulted in the incorporation of the label into t he newly sclerotized cuticle. Hemolymph proteins were synthesized in vivo u sing [C-14]leucine and subsequently double labeled in vivo with [H-3]dopami ne. After sclerotization (7 h post-ecdysis) the cuticle was extirpated, hyd rolyzed and counted. An identical ratio of C-14 to H-3 was found in cuticle extracts as in the double-labeled hemolymph proteins, suggesting that the phenol-bound protein was incorporated in the cuticle unchanged. It appears that the catechol bound to the proteins exists as a beta-glucoside. (C) 199 9 Elsevier Science Inc. All rights reserved.