A lepidopteran pacifastin member: cloning, gene structure, recombinant production, transcript profiling and in vitro activity.
Members of the pacifastin family have been characterized as serine peptidase inhibitors (PI), but their target enzyme(s) are unknown in insects. So far, the structural and biochemical characteristics of pacifastin-like PI have only been studied in locusts. Here we report the molecular identification and functional characterization of a pacifastin-like precursor in a lepidopteran insect, i.e. the silkworm Bombyx mori. The bmpp-1 gene contains 17 exons and codes for two pacifastin-related precursors of different length. The longest splice variant encodes 13 inhibitor domains, more than any other pacifastin-like precursor in arthropods. The second transcript lacks two exons and codes for 11 inhibitor domains. By studying the expression profile of the Bombyx pacifastin-like gene a different expression pattern for the two variants was observed suggesting functional diversification. Next, several PI domains of BMPP-1 were produced and, contrary to locust pacifastin peptides, they were found to be potent inhibitors of both bovine trypsin and chymotrypsin. Surprisingly, the same Bombyx PI are only weak inhibitors of endogenous digestive peptidases, indicating that other peptidases are the in vivo targets. Interestingly, the Bombyx PI inhibit a fungal trypsin-like cuticle degrading enzyme, suggesting a protective function for BMPP-1 against entomopathogenic fungi.
Breugelmans
Bert
B
Department of Animal Physiology and Neurobiology, Zoological Institute K.U. Leuven, Naamsestraat 59, B-3000 Leuven, Belgium. bert.breugelmans@bio.kuleuven.be
Simonet
Gert
G
van Hoef
Vincent
V
Van Soest
Sofie
S
Smagghe
Guy
G
Vanden Broeck
Jozef
J
D000595:Amino Acid Sequence; D000818:Animals; D012831:Bombyx / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology; D003001:Cloning, Molecular; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005091:Exons; D005658:Fungi / Q000187:drug effects; D015870:Gene Expression; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism* / Q000494:pharmacology; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism* / Q000494:pharmacology; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D016415:Sequence Alignment
D004791:Enzyme Inhibitors; D019476:Insect Proteins; D011506:Proteins; D011994:Recombinant Proteins; C106709:pacifastin