Comparative Study On The Activities Of Sialic Acid-binding Lectin And C-type Lectin

Antimicrobial peptides have broad spectrum of efficient bactericidal ability,which is an choice to replace traditional bactericidal drugs antibiotics.Lectins,as an important class of immune glycoproteins in antimicrobial peptides,play a key role in regulating innate and acquired immune system functions.In this study,the sialic acid-binding lectin recombinant protein rVpSabl and C-type lectin recombinant protein rVpCTL were obtained by constructing prokaryotic expression vector according to their gene sequences,and the corresponding activities of the two proteinsVpSabl andVpCTL were studied.The results were as follows:Through Pathogen-associated molecular patterns(PAMPs)binding assay,it was found that the recombinant protein ofVpSabl(rVpSabl)had obvious binding activity to lipopolysaccharide,peptidoglycan,glucan and zymosan in vitro;the recombinant protein ofVpCTL(rVpCTL)had obvious binding activity to lipopolysaccharide and zymosan in vitro,but had no binding activity to peptidoglycan and glucan at low concentration.In addition,the recombinant protein rVpSabl could agglutinate Escherichia coli,Vibrio parahaemolyticus,Vibrio harveyi,Staphylococcus aureus,Pseudomonas putida,Proteus mirabilis and Pichia pastoris;rVpCTL could agglutinate Escherichia coli,Vibrio parahaemolyticus,Vibrio harveyi,Staphylococcus aureus and Pichia pastoris,but it could not agglutinate Pseudomonas putida and Proteus mirabilis.The two lectin proteins showed a wide range of recognition and binding ability.In phagocytic test,the recombinant protein of rVpSabl and rVpCTL both enhanced the phagocytic ability of blood cells,which proved that the two proteins had good antibacterial ability.Immunohistochemical experiments showed thatVpSabl was mainly expressed in the hepatopancreas,gills,and mantle of Philippine clams.Vp Sabl was significantly expressed in the hepatopancreas and widely distributed,and was also significantly expressed in the gill,with the highest level in the mantle and a uniform but low level in the foot.Vp CTL was expressed in the hepatopancreas,gill,mantle and foot,with significant expression and wide distribution in the hepatopancreas and also middle of the gill tissue,wide distribution but low content in the coat membrane,and even distribution but low content in the foot.The similarity of the two lectins in the experimental results indicated that sialic acidbinding lectins and C-type lectins had the common characteristics of lectins,and were important components of innate immune system,with a wide range of PAMPs binding activities and bacterial agglutination properties.The differences between the two lectins indicated that there were differences in tissue distribution and recognition domains between sialic acid binding lectin and C-type lectin.