Molecular Characterization and Gene Expression Profiling ... - CUSAT

Chapter 1
demonstrated to possess specific biochemical characteristics, such as chitin
(Fujimura et al., 2004; Huang et al., 2004) or heparin (Shimazaki et al., 1998;
Andersson et al., 2004) binding abilities. Structure-activity relationship
studies on three synthetic bovine lactoferricin (amino acids 17 to 30) -
derived peptides revealed a significant positive correlation between the pI
values of peptides and their candidicidal activity (Nikawa et al., 2004).
Another study also showed a direct correlation between the ability of
peptides to form complexes with lipid mixtures and their antifungal activity
(Lopez-Garcia et al., 2004).
Mode of action of antifungal peptides
It was demonstrated that the rabbit-defensin NP-2 resulted in
permeabilization of C. albicans (Patterson-Delafield et al., 1980; Lehrer et al.,
1985). Moerman et al. (2002) subsequently demonstrated that α-helical pore-
forming peptides isolated from scorpion venom had antifungal activity.
Using the organic compound SYTOX green, it was demonstrated that the
peptide permeabilizes fungi (Roth et al., 1997). Lee et al. (2002, 2003) have
shown that indolicidin exerts its fungicidal activity by disrupting the
structure of the fungal cell membrane, in a salt-dependent and energy-
independent fashion, via direct interactions with the lipid bilayer. This
contrasts to the situation for bacteria, in which indolicidin, although
membrane active, appears to penetrate cells and act on macromolecular
synthesis (Falla et al., 1996; Subbalakshmi and Sitaram, 1998).
Bovine lactoferricin have shown to result in profound ultrastructural
damage to the cell wall of C. albicans (Bellamy et al., 1993; Park et al., 2004).
The mechanism of action of certain antifungal peptides is still a matter of
debate. The formation of reactive oxygen species has been suggested to be
the crucial step in the fungicidal mechanism of a number of AMPs
(Narasimhan et al., 2001), including histatin 5 and lactoferrin-derived
peptides (Helmerhorst et al., 2001; Lupetti et al., 2002). Helmerhorst et al.
(1999) found that exposure to the cationic peptide histatin 5 caused a
Molecular Characterization and Gene Expression Profiling of Antimicrobial Peptides in Penaeid Shrimps
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