Cm. Elvin et al., CHARACTERIZATION OF A MAJOR PERITROPHIC MEMBRANE-PROTEIN, PERITROPHIN-44, FROM THE LARVAE OF LUCILIA-CUPRINA - CDNA AND DEDUCED AMINO-ACID-SEQUENCES, The Journal of biological chemistry, 271(15), 1996, pp. 8925-8935
The peritrophic membrane is a semi-permeable chitinous matrix lining t
he gut of most insects and is thought to have important roles in the m
aintenance of insect gut structure, facilitation of digestion, and pro
tection from invasion by microrganisms and parasites, Proteins are int
egral components of this matrix, although the structures and functions
of these proteins have not been characterized in any detail, The peri
trophic membrane from the larvae of the fly Lucilia cuprina, the prima
ry agent of cutaneous myiasis in sheep, was shown to contain six major
integral peritrophic membrane proteins, Two of these proteins, a 44-k
Da glycoprotein (peritrophin-44) and a 48-kDa protein (peritrophin-48)
together represent >70% of the total mass of the integral peritrophic
membrane proteins, Peritrophin-44 was purified and its complete amino
acid sequence was determined by cloning and sequencing the DNA comple
mentary to its mRNA The deduced amino acid sequence codes for a protei
n of 356 amino acids containing an amino-terminal signal sequence foll
owed by five similar but nonidentical domains, each of approximately 7
0 amino acids and characterized by a specific register of 6 cysteines,
One of these domains was also present in the noncatalytic regions of
chitinases from Brugia malayi, Manduca sexta, and Chelonus, Peritrophi
n-44 has a uniform distribution throughout the larval peritrophic memb
rane. Reverse transcriptase-polymerase chain reaction detected the exp
ression of peritrophin-44 in all three larval instars but only trace l
evels in adult L. cuprina, The protein binds specifically to tri-N-ace
tyl chitotriose and reacetylated chitosan in vitro, It is concluded th
at the multiple cysteine-rich domains in peritrophin-44 are responsibl
e for binding to chitin, the major constituent of peritrophic membrane
, Peritrophin-44 probably has roles in the maintenance of peritrophic
membrane structure and in the determination of the porosity of the per
itrophic membrane. This report represents the first characterization o
f an insect peritrophic membrane protein.