Abstract
Horseshoe crab is an ancient marine arthropod that, in the absence of a vertebrate-like immune system, relies solely on innate immune responses by defense molecules found in hemolymph plasma and granular hemocytes for host defense. A plasma lectin isolated from the hemolymph of Taiwanese Tachypleus tridentatus recognizes bacteria and lipopolysaccharides (LPSs), yet its structure and mechanism of action remain unclear, largely because of limited availability of horseshoe crabs and the lack of a heterogeneous expression system. In this study, we have successfully expressed and purified a soluble and functional recombinant horseshoe crab plasma lectin (rHPL) in an Escherichia coli system. Interestingly, rHPL bound not only to bacteria and LPSs like the native HPL but also to selective medically important pathogens isolated from clinical specimens, such as Gram-negative Pseudomonas aeruginosa and Klebsiella pneumoniae and Gram-positive Streptococcus pneumoniae serotypes. The binding was demonstrated to occur through a specific molecular interaction with rhamnose in pathogen-associated molecular patterns (PAMPs) on the bacterial surface. Additionally, rHPL inhibited the growth of P. aeruginosa PAO1 in a concentration-dependent manner. The results suggest that a specific protein-glycan interaction between rHPL and rhamnosyl residue may further facilitate development of novel diagnostic and therapeutic strategies for microbial pathogens.
Highlights
Lectins are a group of carbohydrate-binding proteins that recognize specific carbohydrate structures and are widely distributed in living organisms
Comparisons of the chemical structures of reported pathogen-associated molecular patterns (PAMPs) on rHPLinteracting pathogens indicated that Rha was present on all the recognized samples
RHPL could directly interact with Rha at the molecular level as demonstrated by a glycan array and Magnetic Reduction (MR) assay, suggesting that the Rha moiety is a preferred ligand of recombinant horseshoe crab plasma lectin (rHPL)
Summary
Lectins are a group of carbohydrate-binding proteins that recognize specific carbohydrate structures and are widely distributed in living organisms. Based on the structural and sequence similarities of the carbohydrate-recognition domains (CRDs) and the ligand-binding specificities [1], animal lectins are classified into various families such as M-type lectins, P-type lectins, C-type lectins, I-type lectins, and S-type lectins (galectins), as well as calnexin, pentraxins, and tachylectins [2]. They play diverse roles in physiological processes, functioning as cell surface receptors [3], mediating interactions between cells during development and differentiation [4, 5], and recognizing foreign molecules during immune responses [6]. TPL2 shows an 80% sequence identity with TL-3 [12], and both TPL2 and TL-3 show ligand specificity toward lipopolysaccharides (LPSs), O-antigen [10, 12]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
