Diversity of aminopeptidases, derived from four lepidopteran gene duplications, and polycalins expressed in the midgut of Helicoverpa armigera: identification of proteins binding the delta-endotoxin, Cry1Ac of Bacillus thuringiensis.
Helicoverpa armigera midgut proteins that bind the Bacillus thuringiensis (Bt) delta-endotoxin Cry1Ac were purified by affinity chromatography. SDS-PAGE showed that several proteins were eluted with N-acetylgalactosamine and no further proteins were detected after elution with urea. Tandem mass spectral data for tryptic peptides initially indicated that the proteins resembled aminopeptidases (APNs) from other lepidopterans and cDNA sequences for seven APNs were isolated from H. armigera through a combination of cloning with primers derived from predicted peptide sequences and established EST libraries. Phylogenetic analysis showed lepidopteran APN genes in nine clades of which five were part of a lepidopteran-specific radiation. The Cry1Ac-binding proteins were then identified with four of the seven HaAPN genes. Three of those four APNs are likely orthologs of APNs characterised as Cry1Ac-binding proteins in other lepidopterans. The fourth Cry1Ac-binding APN has orthologs not previously identified as Cry1Ac-binding partners. The HaAPN genes were expressed predominantly in the midgut through larval development. Each showed consistent expression along the length of the midgut but five of the genes were expressed at levels about two orders of magnitude greater than the remaining two. The remaining mass spectral data identified sequences encoding polycalin proteins with multiple lipocalin-like domains. A polycalin has only been previously reported in another lepidopteran, Bombyx mori, but polycalins in both species are now linked with binding of Bt Cry toxins. This is the first report of hybrid, lipocalin-like domains in shorter polycalin sequences that are not present in the longest sequence. We propose that these hybrid domains are generated by alternative splicing of the mRNA.
Angelucci
Constanza
C
CSIRO Entomology, PO Box 1700, Canberra, ACT 2601, Australia.
Barrett-Wilt
Gregory A
GA
Hunt
Donald F
DF
Akhurst
Raymond J
RJ
East
Peter D
PD
Gordon
Karl H J
KH
Campbell
Peter M
PM
D000595:Amino Acid Sequence; D000626:Aminopeptidases / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004064:Digestive System / Q000201:enzymology; D004731:Endotoxins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020440:Gene Duplication; D015870:Gene Expression; D006460:Hemolysin Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D007915:Lepidoptera / Q000737:chemistry / Q000145:classification / Q000201:enzymology / Q000235:genetics; D008969:Molecular Sequence Data; D009036:Moths / Q000737:chemistry / Q000145:classification / Q000201:enzymology* / Q000235:genetics; D010802:Phylogeny; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; D019476:Insect Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis; D000626:Aminopeptidases