Molecular Characterization and Gene Expression Profiling ... - CUSAT

Chapter 1
including the microbes associated with acceptable food sources (Simmaco et
al., 1998; Boman, 2000). It appears reasonable to speculate that an individual
could find itself in the midst of microbes against which the peptides of its
species were ineffective, although the individual might suffer, the species
itself could survive through emergence of individuals expressing beneficial
mutations.
A common property of AMPs is their tendency to fold into
amphipathic structures. The diversity of the peptide primary structures is
due to the necessity of the host immunity to successfully adapt to different
environments by retaining its efficacy against specific microbial pathogens.
Hence, the conservation of antimicrobial functions is highly dependent on
the amphipathic properties of AMPs and not necessarily on the retention of
primary sequence homology. Yet amphipathicity is highly influenced by the
amino acid composition and arrangement in the primary sequence, which
affects the specificity of antimicrobial activity in a given environment (Bals et
al., 1998a, 1998b)
One of the surprising features of AMPs is the conservation of
antimicrobial functions despite their structural diversity. As illustrated in
Fig. 1.6, there is a signal sequence that serves to guide the protein to
secretory vesicles. The active form of the peptide is released after protease-
specific digestion (Harwig et al., 1992; Valore and Ganz, 1992; Pestonjamasp
et al., 2001; Shinnar et al., 2003; Murakami et al., 2004). The propeptide is
sometimes used as a basis for classification.
Fig. 1.6 The Gene structure of a typical Antimicrobial Peptide (Adapted from Zaiou and
Gallo, 2002)
Molecular Characterization and Gene Expression Profiling of Antimicrobial Peptides in Penaeid Shrimps
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