Unraveling the genomic structures, conserved functional domains and evolutionary dynamics of beta-defensins in Bubalus bubalis and Ovis aries.

Abstract

Defensins are key innate immune proteins exhibiting pleiotropic functions such as antibacterial activity, antiviral activity, anti-inflammatory activity, immunomodulatory functions, and roles in reproduction. Genomic information inadequately explains the whole gamut of the landscape of β-defensin in Bubalus bubalis and Ovis aries genomes. This study investigates the sequence evaluation and evolutionary relationships of β-defensin with 131 complete sequences in buffalo, sheep, and human. Sequence and domain-based analyses revealed diverse patterns of disulfide bridges and multiple signature patterns, including N- and O-glycosylation sites, N-myristoylation sites, and protein kinase C phosphorylation sites, indicating extensive post-translational regulation involved in various antimicrobial activities, signaling pathways, and reproduction. Phyre2-based 3D structural modeling, followed by PyMOL visualization, revealed β-strands stabilized by cysteine disulfide bonds and a short N-terminal α-helix. Variation analysis of β-defensin sequences identified unique allelic variants with several conserved amino acid positions. All sequences shared the characteristic six conserved cysteine residues, along with conserved glycine (G) in the GXC motif and glutamic acid (E), which contribute to structural stability and proper protein folding. We report sixteen amino acid sites depicting 9 distinct types of mutations within the cysteine residues, with most frequent substitutions of C→S (5/16) and C→P (3/16) amino acids. Phylogenetic and domain-based analyses across humans, sheep, and buffalo revealed eight major clusters, of which cluster I was found to be most diverse (36/131). Altogether, we provide a comprehensive analysis of β-defensin protein sequences revealing conserved features, functional motifs, and evolutionary relationships underpinning the functional role of β-defensins.