Molecular Characterization and Gene Expression Profiling ... - CUSAT

Chapter 2
One can assume that the peptides, bound to the shrimp cuticle tissues
through chitin-binding property carried by the C-terminal domain, exert
antimicrobial activity and initiate opsono-phagocytosis via the free N-
terminal tail. This domain can adopt a conformation upon interaction with
the bacteria membrane, which displays antimicrobial activity. From all
hypotheses, the two domains are likely to have complementary activities,
and their presence in one single peptide would be necessary for its full
activity. Studies are being undertaken to address this question. Penaeidins,
whose N-terminal sequence shares some similarities with plant extensin
modules, may participate in protein–protein interactions and thus display
various functions. Penaeidin chitin binding ability could participate in anti-
microbial activity and in wound healing and chitin assembly. The peptides
may play a role in the protection of the animals during molting cycle, when
the animals are particularly exposed to potential infections. This dual
function of penaeidins is likely determinant for the survival of the animals.
To address this question, it is now under investigation whether the
penaeidins conserve their anti-microbial activity when bound to the shrimp
cuticle (Bachere et al., 2004).
2.1.3.4. Role of penaeidin NH2- and COOH-terminal regions
Penaeidins combine two domains in their overall structure, one
proline-rich and the other cysteine-rich, usually observed in distinct groups
of antimicrobial peptides (Destoumieux et al., 2000a). The overall biological
activity of penaeidin may be associated with distinct properties of their two
characteristic regions.
NH2-terminal region
The penaeidin N-terminal proline-rich region shares sequence
similarities with other proline-rich antimicrobial peptides (Gennaro et al.,
1989; Schnapp et al., 1996). A synthetic peptide corresponding to the N-
terminal proline-rich domain of penaeidin (residues 1–20) was produced and
found to be inactive against both bacterial and fungal strains. Hence, it is
Molecular Characterization and Gene Expression Profiling of Antimicrobial Peptides in Penaeid Shrimps
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