C-Terminal Domain of Hemocyanin, a Major Antimicrobial Protein from Litopenaeus vannamei: Structural Homology with Immunoglobulins and Molecular Diversity

Abstract

Invertebrates rely heavily on immune-like molecules with highly diversified variability so as to counteract infections. However, the mechanisms and the relationship between this variability and functionalities are not well understood. Here, we showed that the C-terminal domain of hemocyanin (HMC) from shrimp Litopenaeus vannamei contained an evolutionary conserved domain with highly variable genetic sequence, which is structurally homologous to immunoglobulin (Ig). This domain is responsible for recognizing and binding to bacteria or red blood cells, initiating agglutination and hemolysis. Furthermore, when HMC is separated into three fractions using anti-human IgM, IgG, or IgA, the subpopulation, which reacted with anti-human IgM (HMC-M), showed the most significant antimicrobial activity. The high potency of HMC-M is a consequence of glycosylation, as it contains high abundance of α-d-mannose relative to α-d-glucose and N-acetyl-d-galactosamine. Thus, the removal of these glycans abolished the antimicrobial activity of HMC-M. Our results present a comprehensive investigation of the role of HMC in fighting against infections through genetic variability and epigenetic modification.

Reduced redox‐dependent mechanism and glucose‐mediated reversal in gentamicin‐resistant Vibrio alginolyticus

“…Strategies managing antibiotic-resistant bacteria include antibioticindependent and -dependent methods. The antibioticindependent method includes vaccines, metabolomereprogramming molecules, phage therapy and antibacterial peptides (Peng et al, 2015a;Du et al, 2017;Pires et al, 2017;Wang et al, 2017;Zeng et al, 2017;Zhang et al, 2017;Jiang et al, 2019). Vaccines stimulate the host's active immunity against bacterial pathogens (Guo et al, 2018;Cheng et al, 2018a;Peng et al, 2018).…”

Identification and characterization of glycosylation sites on Litopenaeus vannamei hemocyanin

“…All these suggest that the Ig‐like domain of hemocyanin possessed immunology function. Further evidence indicated that the Ig‐like domain of hemocyanin could interact with bacteria and had agglutination activity toward E. coli K12, compared with the other domains of hemocyanin . Aside from this, we also previously showed that an 18.4 kDa peptide on the C terminus of small subunit hemocyanin (double underlined in Fig.…”

“…Our previous studies showed that the Ig‐like domain of Penaeus vannamei hemocyanin could react with anti‐human Ig and was also significantly upregulated during Taura syndrome virus infection . All these suggest that the Ig‐like domain of hemocyanin possessed immunology function.…”

“…Moreover, the agglutinative and antibacterial activity of small subunit hemocyanin significantly decreased upon mutation (T537A, S539A, and T542A). Given that we have previously showed that native shrimp hemocyanin had strong bacterial agglutinative and antimicrobial activities , we went on to determine how the agglutinative and antimicrobial activity of the mut‐rHMCs compared with native hemocyanin or wt‐rHMCs. While mut‐rHMCs still had some bacterial agglutinative and antibacterial activities against V. parahaemolyticus and S. aureus , this was significantly reduced compared with native hemocyanin and wt‐rHMCs, that is, about fourfold reduction in agglutinative activity and 0.2‐fold reduction in antibacterial activity (Fig.…”

“…Besides this, our earlier studies suggested that L . vannamei hemocyanin could react with human IgM, IgG, or IgA as an antigen , bind to bacteria and animal erythrocytes as an agglutinin and hemolysin as well as act as an immune‐enhancing protein .…”