S. Schorderet et al., CDNA AND DEDUCED AMINO-ACID-SEQUENCES OF A PERITROPHIC MEMBRANE GLYCOPROTEIN, PERITROPHIN-48, FROM THE LARVAE OF LUCILIA-CUPRINA, Insect biochemistry and molecular biology, 28(2), 1998, pp. 99-111
The gut of most insects is lined,vith a semi-permeable peritrophic mem
brane (or peritrophic matrix) composed of chitin, proteoglycans and pr
oteins. Despite the probable importance of the peritrophic membrane ir
e facilitating the digestive process and protecting insects from invas
ion by micro-organisms and parasites, there has been little characteri
zation of the specific components and their interactions within this a
cellular structure. Here we report the characterization of an integral
peritrophic membrane glycoprotein, peritrophin-48, from the larvae of
the fly Lucilia cuprina, a primary agent of cutaneous myiasis in shee
p. Peritrophin-48 was purified from peritrophic membrane obtained by l
arval culture and its location within the peritrophic: membrane determ
ined by immune-fluorescence and immune-gold localizations. The cDNA co
ding for peritrophin-48 was cloned and sequenced. The deduced amino ac
id sequence codes for a protein of 375 amino acids containing an amino
-terminal signal sequence followed by five similar, but non-identical
domains, each approximately 65-70 amino acids in length and characteri
sed by a specific register of six cysteines. The deduced amino acid se
quence shows significant similarity to two other peritrophic membrane
proteins, peritrophin-95 and peritrophin-44, from the same species. A
reverse transcriptase-PCR approach indicated that there are several hi
ghly related peritrophin-48 genes expressed in each individual. Revers
e transcriptase-PCR also demonstrated the expression of peritrophin-48
in all three larval instars and adults but not pupae or eggs;. Peritr
ophin-48 was expressed only by the cardia and by the larval midgut. A
simple structural model of a basic unit of a type 2 peritrophic membra
ne is presented. (C) 1998 Elsevier Science Ltd. All rights reserved.