Molecular Characterization and Gene Expression Profiling ... - CUSAT

Chapter 2
observed in gills, heart and intestine (Imjongirak et al., 2007; Zhang et al.,
2007; Supungul et al., 2008) but as these tissues are highly vascularised, it is
assumed the transcripts from these organs is due primarily to the
haemocytes.
2.1.1. Anti-lipopolysaccharide factor (ALF)
Anti-lipopolysaccharide factor (ALF), a small basic protein, was
initially isolated and characterized from the haemocytes of horseshoe crabs,
Tachypleus tridentatus (TALF) and Limulus polyphemus (LALF) (Tanaka et al.,
1982). ALFs can bind and neutralize lipopolysaccharide (LPS) and possess
broad spectrum antimicrobial activities. ALF has a strong antibacterial
activity, especially on the growth of gram-negative R type bacteria (Wang et
al., 2002). As most of the infectious bacterial pathogens in shrimp are gram-
negative bacteria, studies on ALF will be more useful in shrimp disease
control. Structurally, ALF contains two conserved cysteine residues
comprising a cluster of positive charged residues within a disulphide loop
that has been defined as the LPS-binding domain (Hoess et al., 1993). The
function of the ALF lies on the positively charged cluster within a disulfide
loop in its primary structure as suggested by Aketagawa et al. (1986). From
the three-dimensional structure of LALF, the amphipathic disulfide loop
binds lipid A and neutralizes the biological effects of LPS (Hoess et al., 1993).
The ALFs from horseshoe crabs, shrimps and crabs also contain the two
highly conserved-cysteine residues and the highly conserved cluster of
positively charged residues within the disulfide loop. The synthetic disulfide
loops from ALFPm3 and ALFSp have been shown unequivocally to be
antimicrobially active, though the actual mechanism is not known
(Somboonwiwat et al., 2005; Imjongjirak et al., 2007).
They are produced and stored in the haemocyte, a prime cell in the
immune system (Destoumieux et al., 2000b; Somboonwiwat et al., 2005;
Burge et al., 2007). The ALF is a small basic protein that has the ability to
Molecular Characterization and Gene Expression Profiling of Antimicrobial Peptides in Penaeid Shrimps
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