Bright Singh, I S; Rosamma, Philip; Chaithanya, E R; Swapna, Antony P; Afsal, V V(Elsevier, June 27, 2012)
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Abstract:
Anti-lipopolysaccharide factors (ALFs), a type of cationic antimicrobial peptides (AMPs), and their derivatives
are becoming predominant candidates for potential drugs in viral and bacterial diseases. This study
reports the first ALF from the mud crab Scylla tranquebarica (StALF, JQ899453) and the second ALF isoform
from the blue swimmer crab Portunus pelagicus (PpALF2, JQ899452). Both sequences encoded for precursor
molecules, starting with a signal peptide containing 26 amino acid residues, followed by a highly
cationic mature peptide, containing two conserved cysteine residues flanking a putative lipopolysaccharide
(LPS)-binding domain. BLAST analysis revealed that both PpALF2 and StALF exhibited significant
similarity with crustacean ALF sequences. The predicted molecular mass of the mature ALFs was 11.2 kDa
with an estimated pI of 10.0. PpALF2 and StALF also showed the typical pattern of alternating hydrophobic
and hydrophilic residues in their putative disulphide loop, suggesting that they comprise the same
functional domain. Phylogenetic analysis showed that PpALF2 and StALF have similar evolutionary status
and they were phylogenetically ancient immune effector molecules which may play an essential role in
the host defense mechanism. The spatial structures of PpALF2 and StALF possessed four beta-strands and
two alpha-helices. The results indicated that there were more than one ALF involved in crab immunity
against various pathogens. ALFs would provide candidate promising therapeutic or prophylactic agents
in health management and diseases control in crustacean aquaculture