Amino acid sequence variations and 3D structure analysis of Ascaris suum antibacterial factor proteins

• Main Authors: Oyong, Glenn G., Mohammad, Ehsan Zangeneh
• Format: text
• Published: Animo Repository 2011
• Subjects: Nematodes; Antibacterial agents; Biochemistry, Biophysics, and Structural Biology; Biology
• Online Access: https://animorepository.dlsu.edu.ph/faculty_research/8594
• Institution: De La Salle University

A large number of invertebrates have recently been used as models in the study of innate immunity. Previous studies report that antibacterial property is exhibited in the pseudocoelom of the nematode Ascaris suum. The antibacterial activity was due to a heat-stable and trypish-sensitive protein designated as ASABF (Ascaris suum Antibacterial Factor). Several studies have been carried out in the purification, determination of primary structure and cDNA cloning of ASBF. Transcription induction studies reported that ASBF occurs as a type form α, followed by five recently identified novel members namely β, у, δ, ε and ζ. Amino acid sequence alignment revealed several amino acid changes except the presence of six highly conserved cysteine residues also previously identified in insect/arthropod defensis. Until recently, there are only few studies which investigated the three-dimensional structure of ASABF proteins. This paper presents molecular comparison between ASABF proteins by computer modeling. Predict protein structural analysis revealed the presence of two major beta sheets and one alpha helix stabilized by intra-disulfide bonds confirmed by Ramachandran plots generated through NOC program. Surface residue accessibility revealed more than 50% exposed basic residues imparting a net surface positive charge - a major advantage towards affinity to the negatively charged bacterial peptidoglycan wall. Prediction of motifs showed possible three myristoylation sites which may explain the key mechanism behind antibacterial activity. Analyzing molecular changes through structure molecular graphics and model building analysis further help in the understanding of mechanisms involved in antibacterial property and subsequent drug design.