University of Guilan
Abstract: (2 Views)
The OLD101/SAL1 enzyme family plays an important role in plant physiology and stress adaptation in Arabidopsis thaliana, owing to its dual nucleotidase and phosphatase activities. This study applies an integrative in silico framework to investigate the evolutionary, structural, and functional properties of the SAL1 family, with particular emphasis on the impact of the old101 point mutation as a representative perturbation of SAL1 activity. Analysis of this family led to the identification of nine homologous proteins harboring a conserved inositol monophosphatase (Sun et al.) domain. Despite sharing similar EC classifications, these enzymes exhibit distinct functional domains, while phosphoadenosine phosphate (PAP) remains a common substrate across most family members. Phylogenetic reconstruction places AtSAL1 in a tightly supported clade with AtSAL3.1, AtSAL4, and AtSAL2.1, whereas IMPL and VTC4 proteins form more distantly related lineages, reflecting divergent evolutionary trajectories. Pathway-level analysis positions SAL1 and its paralogs at the intersection of phosphate, inositol phosphate, and sulfur metabolic networks, where they function as central hubs in the metabolic network. Examination of miRNA–mRNA interactions indicates that the old101 mutation does not reconfigure post-transcriptional regulatory patterns, preserving the overall miRNA-mediated control of SAL1 transcripts. Structural modeling delineates the Mg²⁺-coordinated region as the principal catalytic pocket of both SAL1 and the mutant variant, thereby providing a suitable basis for ligand-binding analyses. Molecular docking further reveals that although the old101 mutation induces localized rearrangements within the binding pocket and alters interaction dynamics, ligand-binding capability is preserved and enzymatic activity is not completely disrupted. Collectively, these findings underscore SAL1 as a key integrative node linking phosphate, sulfur, and inositol signaling pathways, and offer a coherent mechanistic framework for predicting how structural perturbations modulate ligand binding without fully compromising catalytic competence.
Article number: 4
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