Abstract:
Bactericidal permeability-increasing protein (BPI)/lipopolysaccharide (LPS) binding proteins (LBPs) are
well-known proteins that play an indispensable role in host antimicrobial defense. Herein, we report a
homolog of BPI/LBP from black rockfish (Sebastes schlegelii) (designated as RfBPI/LBP) and characterize its
structural and functional features at the molecular level. We identified the putative complete open
reading frame (1422 bp) of RfLBP that encodes a 474 amino acid protein with a predicted molecular mass
of ~51.5 kDa. The primary protein sequence of RfBPI/LBP contains domain features of BPI/LBP family
proteins and shares significant sequence consistency with its homologs. Our phylogenetic analysis clearly
demonstrated the vertebrate ancestral origin of RfBPI/LBP, further reinforcing its evolutionary relationship with teleostean homologs. Recombinant RfBPI/LBP demonstrated in vitro LPS-binding activity and
antibacterial activity against Escherichia coli, but not against Streptococcus iniae. Moreover, RfBPI/LBP
exhibited temporal transcriptional activation against pathogens and pathogen-associated molecular
patterns. Collectively, our findings suggest that RfBPI/LBP plays an essential role in host antimicrobial
defense, plausibly through selective eradication of invading bacteria
