Effect of Amino Acid Substitution in the Penaeus monodon LGBP and Specificity Through Mutational Analysis
Jeyachandran Sivakamavalli, Chandrabose Selvaraj, Sanjeev Kumar Singh, Kiyun Park, Ihn-Sil Kwak, Baskaraingam Vaseeharan
International Journal of Peptide Research and Therapeutics
Lipopolysaccharide and β-1,3-glucan-binding protein (LGBP) is a pattern recognition protein (PRP) purified from the Penaeus monodon by Blue-Sepharose, Phenyl-Sepharose followed by Sephadex G-100 chromatography. P. monodon LGBP consist of 36 and 48 kDa subunits on 10% SDS-PAGE under reducing and non-reducing conditions respectively. Purified P. monodon LGBP agglutinates the fungal pathogen Candida glabrata, due to the presence of β-glucan (βG) on its surface. This agglutination was cross checked with the in silico docking analysis of LGBP-βG and LGBP-laminarin (isomeric form βG) interaction. As part of a strategy, to determine the precise role of P. monodon LGBP (Pm-LGBP) in pattern recognition mechanism mutations were introduced by in silico approach. In crustacean LGBP, RGD motif (Arg, Gly, Asp) plays the vital role in the cell adhesion and pattern recognition mechanism. Role of Asp in RGD motif was determined through amino acid substitution, introduction of a specific mutation D134K into a central area of the sugar-binding (βG) site resulted in complete loss of pathogen recognition and binding of Pm-LGBP to βG. These results demonstrate that, the RGD motif of Asp134 is essential for sugar binding in P. monodon. To our knowledge, P. monodon D134K is the first mutant shrimp LGBP which is unable to bind with the sugar residues. This mutant could be useful in the discovery of actual function of Pm-LGBP in the recognition of homologous symbionts.
Circular dichroism, Thermal stability, Secondary structure, Biochemistry