2020): Discovery of potential multi-target-directed ligands by targeting host-specific SARS-CoV-2 structurally conserved main protease, Journal of Biomolecular Structure and Dynamics, ABSTRACT Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has resulted in the current COVID-19 pandemic. Worldwide this disease has infected over 2.5 million individuals with a mortality rate ranging from 5 to 10%. There are several efforts going on in the drug discovery to control the SARS-CoV-2 viral infection. The main protease (M Pro ) plays a critical role in viral replication and maturation, thus can serve as the primary drug target. To understand the structural evolution of M Pro , we have performed phylogenetic and Sequence Similarity Network analysis, that depicted divergence of Coronaviridae M Pro in five clusters specific to viral hosts. This clustering was corroborated with the comparison of M Pro structures. Furthermore, it has been observed that backbone and binding site conformations are conserved despite variation in some of the residues. These attributes can be exploited to repurpose available viral protease inhibitors against SARS-CoV-2 M Pro . In agreement with this, we performed screening of $7100 molecules including active ingredients present in the Ayurvedic antitussive medicines, anti-viral phytochemicals and synthetic anti-virals against SARS-CoV-2 M Pro as the primary target. We identified several natural molecules like d-viniferin, myricitrin, taiwanhomoflavone A, lactucopicrin 15-oxalate, nympholide A, afzelin, biorobin, hesperidin and phyllaemblicin B that strongly binds to SARS-CoV-2 M Pro . Intrestingly, these molecules also showed strong binding with other potential targets of SARS-CoV-2 infection like viral receptor human angiotensin-converting enzyme 2 (hACE-2) and RNA dependent RNA polymerase (RdRp). We anticipate that our approach for identification of multi-target-directed ligand will provide new avenues for drug discovery against SARS-CoV-2 infection. ARTICLE HISTORY

Collagen fibrils are central to the molecular organization of the extracellular matrix (ECM) and to defining the cellular microenvironment. Glycation of collagen fibrils is known to impact on cell adhesion and migration in the context of cancer and in model studies, glycation of collagen molecules has been shown to affect the binding of other ECM components to collagen. Here we use TEM to show that ribose-5-phosphate (R5P) glycation of collagen fibrils-potentially important in the microenvironment of actively dividing cells, such as cancer cells-disrupts the longitudinal ordering of the molecules in collagen fibrils and, using KFM and FLiM, that R5P-glycated collagen fibrils have a more negative surface charge than unglycated fibrils. Altered molecular arrangement can be expected to impact on the accessibility of cell adhesion sites and altered fibril surface charge on the integrity of the extracellular matrix structure surrounding glycated collagen fibrils. Both effects are highly relevant for cell adhesion and migration within the tumour microenvironment. Collagen fibrils are central to the molecular organization of the extracellular matrix (ECM) and thus to defining the cellular microenvironment 1,2. Cells bind to specific GXOGER sequences on collagen fibrils via non-covalent interactions with transmembrane integrin receptors for both adhesion and migration purposes 3-10 , signal transduction via integrin-collagen binding being relevant for cell growth and differentiation 11. The extent of integrin binding to collagen-and thus the strength of signalling-is dependent on the degree of exposure of the relevant GXOGER molecular sequences on the collagen fibril surface, which in turn depends on the arrangement of collagen molecules within the fibrils. Non-covalent interactions between specific amino acid sequences in collagen molecules and other extracellular matrix (ECM) proteins also direct the organisation of molecules around collagen fibrils and so are crucial in both the initial self-assembly of the ECM and in maintaining its structural integrity. Thus, the physicochemical and structural state of collagen fibrils is highly relevant to cell growth and mobility and to the overall spatial organization of the extracellular matrix networks. Collagen fibrils are subject to non-enzymatic glycation reactions because they are relatively accessible to exogenous sugars and other aldehydes. Glycation is a spontaneous non-enzymatic reaction between carbonyl groups of reducing sugars and amine groups of proteins, lipids or nucleic acids, occurring in all living systems 12,13. The glycation reactions between collagen and sugars are highly complex, with many possible sugar-adduct intermediate products and further reactions steps to form so-called advanced glycation endproducts (AGEs), the latter of which includes intermolecular crosslinks 14,15. The glycation reaction begins with Schiff base formation at lysine sidechain amines and then Amadori rearrangement to a variety of sugar adducts of Lys through a range of facile intra...

Advanced glycation end products (AGEs) are formed when glucose reacts nonenzymatically with proteins; these modifications are implicated in aging and pathogenesis of many age-related diseases including type II diabetes, atherosclerosis, and neurodegenerative disorders. Thus, pharmaceutical interventions that can reduce AGEs may delay age-onset diseases and extend lifespan. Using LC-MSE, we show that rifampicin (RIF) reduces glycation of important cellular proteins in vivo and consequently increases lifespan in Caenorhabditis elegans by up to 60%. RIF analog rifamycin SV (RSV) possesses similar properties, while rifaximin (RMN) lacks antiglycation activity and therefore fails to affect lifespan positively. The efficacy of RIF and RSV as potent antiglycating agents may be attributed to the presence of a p-dihydroxyl moiety that can potentially undergo spontaneous oxidation to yield highly reactive p-quinone structures, a feature absent in RMN. We also show that supplementing rifampicin late in adulthood is sufficient to increase lifespan. For its effect on longevity, rifampicin requires DAF-18 (nematode PTEN) as well as JNK-1 and activates DAF-16, the FOXO homolog. Interestingly, the drug treatment modulates transcription of a different subset of DAF-16 target genes, those not controlled by the conserved Insulin-IGF-1-like signaling pathway. RIF failed to increase the lifespan of daf-16 null mutant despite reducing glycation, showing thereby that DAF-16 may not directly affect AGE formation. Together, our data suggest that the dual ability to reduce glycation in vivo and activate prolongevity processes through DAF-16 makes RIF and RSV effective lifespan-extending interventions.

Glycation induced protein aggregation has been implicated in the development of diabetic complications and neurodegenerative diseases. These aggregates are known to be resistant to proteolytic digestion. Here we report the identification of protease resistant proteins from the streptozotocin induced diabetic rat kidney, which included enzymes in glucose metabolism and stress response proteins. These protease resistant proteins were characterized to be advanced glycation end products modified and ubiquitinated by immunological and mass spectrometry analysis. Further, diabetic rat kidney exhibited significantly impaired proteasomal activity. The functional analysis of identified physiologically important enzymes showed that their activity was reduced in diabetic condition. Loss of functional activity of these proteins was compensated by enhanced gene expression. Aggregation prone regions were predicted by in silico analysis and compared with advanced glycation end products modification sites. These findings suggested that the accumulation of protein aggregates is an inevitable consequence of impaired proteasomal activity and protease resistance due to advanced glycation end products modification. Molecular & Cellular

Collagen fibrils are a major component of the extracellular matrix. They form nanometer-scale “cables” acting as a scaffold for cells in animal tissues and are widely used in tissue-engineering. Besides controlling their structure and mechanical properties, it is crucial to have information of their surface charge, as this affects how cells attach to the scaffold. Here, we employed Kelvin-probe Force Microscopy to determine the electrostatic surface potential at the single-fibril level and investigated how glutaraldehyde, a well-established protein cross-linking agent, shifts the surface charge to more negative values without disrupting the fibrils themselves. This shift can be interpreted as the result of the reaction between the carbonyl groups of glutaraldehyde and the amine groups of collagen. It reduces the overall density of positively charged amine groups on the collagen fibril surface and, ultimately, results in the observed negative shift of the surface potential measured. Reactions between carbonyl-containing compounds and proteins are considered the first step in glycation, the non-enzymatic reaction between sugars and proteins. It is conceivable that similar charge shifts happen in vivo caused by sugars, which could have serious implications on age-related diseases such as diabetes and which has been hypothesised for many years.