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Degradation of aberrant proteins by larval tobacco hornworm, Manduca sexta L. (Sphingidae)
Author(s) -
Rosenthal Gerald A.,
Dahlman Douglas L.
Publication year - 1988
Publication title -
archives of insect biochemistry and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.576
H-Index - 66
eISSN - 1520-6327
pISSN - 0739-4462
DOI - 10.1002/arch.940080303
Subject(s) - manduca sexta , sphingidae , biology , proteases , biochemistry , manduca , protease , trypsin , canavanine , protein degradation , amino acid , enzyme , insect , arginine , botany
The tobacco hornworm Manduca sexta (Sphingidae) readily incorporates L ‐canavanine, the L ‐2‐amino‐4‐(guanidinooxy)butyric acid structural analog of L ‐arginine, into newly synthesized proteins. As a result, the developing fifth‐instar larva produces structurally aberrant canavanyl proteins that can exhibit severely impaired function. This situation is exacerbated by canavanine's ability to stimulate de novo protein synthesis. M. sexta larvae can respond to anomalous protein production by degrading canavanyl proteins nearly five times faster than normal proteins. The proteases of this insect can distinguish between normal and anomalous proteins and thereby avoid destruction of essential macromolecules. Aberrant protein degradative activity is not dependent upon de novo protein synthesis induced by canavanyl proteins. The fat body appears to be the source of proteases that degrade aberrant proteins; degradation is curtailed in the presence of sulfhydryl protease inhibitors as well as inhibitors of trypsin‐like activity.