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Molecular characterization and phylogenetic analysis of an anti-lipopolysaccharide factor from the crucifix crab, Charybdis feriatus

Authors Sruthy K, Nair A, Cubelio SS, Bright Singh IS, Philip R

Received 1 May 2015

Accepted for publication 4 August 2015

Published 21 September 2015 Volume 2015:7 Pages 149—156


Checked for plagiarism Yes

Review by Single-blind

Peer reviewer comments 3

Editor who approved publication: Dr Peter Koulen

KS Sruthy,1 Aishwarya Nair,1 Sherine Sonia Cubelio,2 IS Bright Singh,3 Rosamma Philip1

1Department of Marine Biology, Microbiology and Biochemistry, School of Marine Sciences, Cochin University of Science and Technology, 2Centre for Marine Living Resources and Ecology, Ministry of Earth Sciences, Government of India, 3National Centre for Aquatic Animal Health, Cochin University of Science and Technology, Kochi, Kerala, India

Abstract: Antimicrobial peptides are small cationic, gene-encoded, amphipathic, host defense peptides with a ubiquitous distribution in all living kingdoms. They are <10 kDa in size, with 15–100 amino acids having a net positive charge of +2 to +9. Anti-lipopolysaccharide factor (ALF) is a cationic antimicrobial peptide which constitutes one of the key effector molecules in the innate immune system of crustaceans, and is capable of binding and neutralizing lipopolysaccharides. In the present study, an ALF homolog (Charybdis feriatus [Cf]-ALF1)-encoding cDNA sequence from the hemocytes of the crucifix crab, C. feriatus, was cloned, identified, and characterized. The deduced peptide of Cf-ALF1 encoded for a 123 amino acid peptide with a 97 residue mature peptide (11.16 kDa) that had a net charge of +10. Two conserved cysteine residues and a putative lipopolysaccharide binding domain were observed in the Cf-ALF1 mature peptide. BLAST analysis of Cf-ALF1 nucleotides showed a 99% similarity to Scylla serrata. The spatial structure of Cf-ALF1 was composed of three α-helices packed against a four-strand β-sheet. Two of these helices were linked by a disulfide bond to form an amphipathic loop similar to the structure of anti-lipopolysaccharide factor isoform 3 from Penaeus monodon (ALF-Pm3). All these features suggest that Cf-ALF1 could play a significant role in the innate immune defense mechanism of C. feriatus.

Keywords: antimicrobial peptides, crab, innate immunity, Charybdis feriatus, anti-lipopolysaccharide factor

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