Characteristic and antibacterial effect of a histone H2A and its preliminary roles in extracellular traps in manila clam Ruditapes philippinarum

In the present study, a histone H2A (designed as RpH2A) was identified and characterized from clam Ruditapes philippinarum , and its open reading frame (ORF) was of 387 bp encoding a polypeptide of 128 amino acids. The deduced amino acid sequence of RpH2A shared high identities ranging from 57.1% to 96.1% with that of other identified H2A. The mRNA expression of RpH2A was up-regulated significantly after Vibrio anguillarum challenge. The recombinant RpH2A protein (rRpH2A) displayed significantly binding affinity to lipopolysaccharide (LPS) and peptidoglycan (PGN) in vitro , and also exhibited antimicrobial properties against Escherichia coli . In addition, the antimicrobial RpH2A was shown to co-localize with extracellular traps (ETs) released from hemocytes induced by E. coli , suggesting that RpH2A might contribute to eliminate invading bacteria in clam ETs. Altogether, our data revealed that RpH2A could function as antimicrobial peptides, which might play a crucial role in the immune responses of hemocytes ETs in clams. • A conserved H2A histone (RpH2A) was identified from Ruditapes philippinarum. • rRpH2A displayed significantly binding activity to both LPS and PGN. • rRpH2A exhibited antimicrobial properties against Escherichia coli. • RpH2A was a component of extracellular traps (ETs) released from hemocytes after E. coli infection.