ИСТИНА

Thiamin (vitamin B1) deficiency leads to neurological disorders corrected by thiamin administration, with high doses of thiamin improving cognition in patients with neurodegenerative diseases. In addition to thiamin diphosphate, the well-known coenzyme of central metabolism, living systems synthesize the non-coenzyme derivatives, such as thiamin triphosphate and adenylated thiamine triphosphate, suggested to be involved in neurotransmission and/or stress response. However, poor identification of biosynthetic enzymes and molecular targets of the non-coenzyme derivatives impedes understanding molecular mechanisms of action and pharmacological potential of these compounds. Our work aims at molecular identification of proteins and pathways mediating the non-coenzyme action of thiamin. To address this goal, we defined the thiamin-binding structural motifs by using resolved structures of protein complexes with thiamin, its natural derivatives or biosynthetic precursors, and performed the PROSITE scan of the protein/genome databases against the 21 motifs created. Conservation of a motif within homologous proteins and/or co-occurrence of different thiamin-binding motifs within one protein were considered to heighten functional significance of the motif in the PROSITE hits. Examination of available 3D structures addressed the question if spatial configuration of the thiamin-binding motif in a predicted protein enables the binding function. Human proteome comprising proteins possessing the thiamin-binding motifs was analyzed by DAVID. The most enriched functional annotation terms and protein clusters of the proteome were related to extracellular matrix, signaling and post-translational modifications, supporting experimental data on the thiamin deficiency affecting cell junctions and signal-related protein modifications. Comparison of the predicted and experimental thiamin-binding proteomes pointed to enzymes of central metabolism possessing the functionally competent thiamin-binding motifs near the active and/or regulatory sites. Kinetic assays confirmed allosteric (non-coenzyme) regulation of the enzymes by thiamin and/or derivatives, providing proof-of-concept for the bioinformatics-guided identification of the thiamin-dependent proteins. Thus, our structure-based predictions help identification of pharmacological targets of thiamin and derivatives.