Title

Molt-Cycle Correlated Patterns of Synthesis of Integumentary Proteins in the Land Crab Gecarcinus Lateralis

Document Type

Article

Publication Date

1-1-1988

Description

We describe here an in vitro investigation of the formation and dissolution of the crustacean exoskeleton by the integumentary tissues of the Bermuda land crab Gecarcinus lateralis. We focus on the synthesis of proteins during the formation of a new exoskeleton and the degradation of an old one. Tissues of animals at different stages of the molt cycle were labeled in vitro with radioamino acids following which proteins were analyzed by a number of methods. From their patterns of synthesis, crab integumentary proteins (CIPs) may be classified into five groups. Group I CIPs include many over a wide range of molecular weights that are synthesized at a relatively constant rate throughout the molt cycle and are designated "housekeeping" proteins. The synthesis of a subset of such housekeeping CIPs (Group II) increases from two- to fivefold during proecdysis when formation of the epicuticle and exocuticle of the new exoskeleton is in progress. Group III CIPs are synthesized intermittently from very early proecdysis, when degradation of the old exoskeleton begins, and throughout the remainder of proecdysis. Groups IV and V first appear at stages in the molt cycle that suggest that they may be structural components of the new exoskeleton. Group IV CIPs, which are synthesized at the time of epi- and exocuticle formation, have a wide range of sizes. Group V CIPs, which comprise several very large proteins, are synthesized in stage B of metecdysis at the time when the formation of the endocuticle begins. A number of CIPs cross-react strongly with polyclonal antibodies to cuticle proteins of pupae and larvae of the tobacco hornworm Manduca sexta, indicating that exoskeletal/cuticle proteins of these two classes of arthropods, the Insecta and Crustacea, share epitopes. Whether the common epitopes relate to amino acid sequences or structural properties remains to be determined.

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