Silkworm, cecropia

Recently, a variety of natural peptides that form transmembrane channels have been identified and characterized. Melittin (Figure 10.35) is a bee venom toxin peptide of 26 residues. The cecropins are peptides induced in Hyalophora cecropia (Figure 10.36) and other related silkworms when challenged by bacterial infections. These peptides are thought to form m-helical aggregates in mem-... 

Williams, C. 1967. The juvenile hormone. II. Its role in the endocrine control of molting, pupation, and adult development in the cecropia silkworm. Biol. Bull. Woods Hole, 121, 572-585. 

In the Lepidoptera, four other homologs have been isolated in addition to JH III. The ethyl branched homologs, juvenile hormone I (JH I), methyl-10/ , 1 l-epoxy-7-ethyl-3,l 1-dimethyl-2,6-tridecadienoate, and juvenile hormone II, methyl-10/ , 1 l-epoxy-3,7,11-trimethyl-2,6-tridecadienoate, and their corresponding acids predominate in this order [14, 15, 16]. Two additional homologs, juvenile hormone 0 (JH 0), 10/ , 11-epoxy-3,7-diethyl-1 l-methyl-2,6-tridecadienoate, and 4-methyl JH I have been isolated from embryos of the tobacco homworm, Manduca sexta JH 0 has also been isolated from males of the silkworm, Hylophora cecropia [17, 18, 19]. In higher Diptera (flies), a unique JH bisepoxide, methyl-6,7,10,1 l-bisepoxy-3,7,11-trimethyl 2 -dodecenoate, has been isolated and appears to be the principle JH of some species in this order [20]. 

This pathway or variations of it occur in other insect species. The ethyl branches of the higher JH homologs found in the Lepidoptera (Fig. (1)) are derived from isoleucine and valine which are first metabolized to propionate and then incorporated, instead of acetate, in the early steps of biosynthesis [72, 73], The sequence of the final steps of JH biosynthesis may also be different in these insect species. In the adult female CA of some Lepidoptera, epoxidation of famesoic acid to the JH acid occurs before the final methylation step [64,65, 71]. Interestingly, in larval stages of the tobacco homworm, M. sexta, and adult males of the silkworm, Hyalophora cecropia, the CA synthesize and release JH acids into the... 

Cecropins. Cecropins (169) were isolated from the larval hemolymph of the giant silkworm moth, Hyalophora cecropia, on the basis of their antibacterial activity subsequent to bacterial injection. Cecropins are also produced by Drosophila (170) and the larva of the tobacco homworm, Manduca sexta (110). Similar compounds called sarcotoxins (171) are produced by the flesh fly, Sarcophaga. Cecropins (169) are specific for prokaryotic cell lysis in contrast to melittin, which lyses eukaryotic cell membranes as well. Cecropins are characterized structurally by a concentration of basic... 

Another example of a sesquiterpene-derived insect juvenile hormone is that of the giant silkworm moth, Hyalophora cecropia (Fig. 21.18). Several juvenile hormone mimics have been found in plants (Bowers, 1985,1991,1992 Fraga, 1991 Menn and Beroza, 1972). 

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