Tej P. Singh - Work

Work

The three-dimensional structures of various proteins including lactoperoxidase, Peptidoglycan recognition Protein and lactoferrin from several species, ribosome inactivating proteins, bifunctional inhibitor proteins from plant seeds and various serine proteases and their inhibitors have been determined by his group. The elaborate structural studies of proteins from several important systems as potential drug targets such as phospholipase A2, cyclooxygenase, lipoxygenase, endothelin receptor, endothelin converting enzyme, breast cancer regression proteins and matrix metanosomal proteins as well as their complexes with natural and designed synthetic ligands have been carried out. His laboratory has submitted more than 301 sets of proteins structure coordinates in the protein data bank (PDB) which makes it the highest number in India. Initially, he had contributed significantly on the structure - function studies of a number of antipyretic, analgesic and anti-inflammatory agents and then on antibacterial sufonamides and their derivatives. He had developed the rules of peptide design with alpha, beta – dehydro - amino acids through extensive studies using syntheses, and X-ray and NMR structure determinations. These design rules are being exploited for making specific peptides to act as tight inhibitors of target enzymes and potent antagonists of target receptors for eventually leading to useful therapeutic agents.

As part of his protein structural studies, a large number of structures of lactoferrin proteins from various species in iron-saturated and apo-forms as well as those of its proteolytically generated monoferric functional N- and C-lobes have been determined in his laboratory through which it was demonstrated that large-scale conformational changes occur in the structures of lactoferrins upon iron-binding and iron-release, cations other than ferric ion also bind to the iron-binding cleft but with lower affinity, similarly anions other than carbonate/bicarbonate can also bind with reduced potency, and bilobal lactoferrin can be converted into two functional N-terminal and C-terminal lobes with proteinase K. These studies have provided valuable insights into the structural basis of iron-binding and iron-release in lactoferrins and their roles as antibacterial agents and in other therapeutic applications. While carrying out enzymatic cleavage of lactoferrin proteins, a novel antifungal decapeptide was discovered whose excellent potency against bacterial infections has been established.

His group has carried out extensive structural studies of phospholipase A2 enzymes and their complexes with various natural compounds, substrate analogues, non-steroidal anti-inflammatory agents and designed peptides. The new molecules have also been designed against cyclooxygenase and lypoxygenase. The enzymes phospholipase A2, cyclooxygenase and lypoxygenase are involved in the production of pro-inflammatory compounds collectively called as eicosanoids. He has already developed several highly potent inhibitors that are under consideration for further evaluation as anti-inflammatory agents. His group has been practicing the rational approach of structure-based drug design for developing therapeutic agents against various inflammatory disorders such as rheumatism and arthritis using PLA2, COX-2 and LOX enzymes as macromolecular targets.

His group has determined the crystal structures of several secretory glycoproteins isolated from dry secretions of various mammalian species including humans. This is a new class of proteins, first time detected whose functions and structures were unknown. These proteins are implicated as protective signaling factors in the large-scale tissue remodeling processes. Their role in the breast cancers as protective factors for the breast cancer cells makes them important targets for structure - based drug design and offers opportunities for developing new therapeutic agents against breast cancer. He has been able to design several peptides that bind to these proteins with potencies ranging up to 10-7 M.

The crystal structures of the complexes of these proteins with designed peptides have helped in identifying the site of binding in this protein. The structures of the complexes with various oligosachharides have provided information about the potencies of sugar binding. It also indicated the type and nature of sugars that will bind to this class of proteins specifically. Furthermore, several crystal structures of the ternary complexes of these proteins with peptides and sugars have helped in understanding the mode of binding of these proteins to cell surface receptors. He initiated a new programme on Clinical Proteomics in which it is intended to characterize all the proteins that are expressed during various patho/physiological conditions. The newly identified proteins will either be useful as biomarkers or they may be associated with the progression of diseases making them important targets for drug design. He has published more than 350 research papers in the leading journals.