Serine protease identification (in vitro) and molecular structure predictions (in silico) from a phytopathogenic fungus,Alternaria solani

Abstract

Serine proteases are involved in an enormous number of biological processes. The present study aims at characterizing three‐dimensional (3D) molecular architecture of serine proteases from early blight pathogen, Alternaria solani that are hypothesized to be markers of phytopathogenicity. A serine protease was purified to homogeneity and MALDI‐TOF‐MS/MS analysis revealed that protease produced by A. solani belongs to alkaline serine proteases (AsP). AsP is made up of 403 amino acid residues with molecular weight of 42.1 kDa (Isoelectric point – 6.51) and its molecular formula was C1859H2930N516O595S4. AsP structure model was built based on its comparative homology with serine protease using the program, MODELER. AsP had 16 β‐sheets and 10 α‐helices, with Ser350 (G347–G357), Asp158 (D158–H169), and His193 (H193–G203) in separate turn/coil structures. Biological metal binding region situated near 6th‐helix and His193 residue is responsible for metal binding site. Also, calcium ion (Ca2+) is coordinated by the carboxyl groups of Lys84, Ile85, Lys86, Asp87, Phe88, Ala89, Ala90 (K84–A90) for first Ca2+ binding site and carbonyl oxygen atom of Lys244, Gly245, Arg246, Thr247, Lys248, Lys249, and Ala250 (K244–A250), for second Ca2+ binding site. Moreover, Ramachandran plot analysis of protein residues falling into most favored secondary structures were determined (83.3%). The predicted molecular 3D structural model was further verified using PROCHECK, ERRAT, and VADAR servers to confirm the geometry and stereo‐chemical parameters of the molecular structural design. The functional analysis of AsP 3D molecular structure predictions familiar in the current study may provide a new perspective in the understanding and identification of antifungal protease inhibitor designing.

Microwave Characterization of Hydrophilic and Hydrophobic Plant Pathogenic Fungi Using Open-Ended Coaxial Probe

“…We also noticed the dielectric constant and conductivity behavior of A. solani are higher than any other foliar causing fungal pathogen tested. Although some studies have reported that cytoplasmic components of A. solani are hydrophobic, others have indicated polar and hydrophilic amino acids in its cytoplasm [43], [44]. In fact, the cationic and hydrophobic features are associated with microbial peptides interacting primarily with negatively charged biomembranes [45], [46]; such membrane effect is pronounced at low frequency.…”

Current Status of Early Blight Resistance in Tomato: An Update

“…Extracellular proteases are key enzymes produced by fungi during the host-pathogen interaction and are involved in growth, development, survival and pathogenicity [ 31 ]. The presence of an extracellular serine protease and metalloprotease was recently found to be secreted by A. solani and proposed to be involved in phytopathogenicity [ 32 , 33 ]. However, additional molecular studies are needed to demonstrate that they play a role in virulence.…”

Integrative transcriptome analysis revealed the pathogenic molecular basis of Rhizoctonia solani AG-3 TB at three progressive stages of infection

“…The fungal deuterolysin metalloprotease (M35) family was reported to be involved in cell wall degradation, epidermal growth inhibition, and cell activity of insects ( Huang et al, 2020 ). The serine protease is an important pathogenic marker for Alternaria solani ( Chandrasekaran et al, 2014 ). We presumed that these deduced secreted proteins in pathogen of tobacco target spot may serve as potential effectors that may play important roles in the pathogenicity of fungus, and remains to be further investigated in the following work.…”