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1,693 results on '"Srivastava, Saurabh"'

59. Sialoglycan-binding patterns of bacterial AB5 toxin B subunits correlate with host range and toxicity, indicating evolution independent of A subunits.

Author

Khan, Naazneen, Sasmal, Aniruddha, Khedri, Zahra, Secrest, Patrick, Verhagen, Andrea, Srivastava, Saurabh, Varki, Nissi, Chen, Xi, Yu, Hai, Beddoe, Travis, Paton, Adrienne W, Paton, James C, and Varki, Ajit

Subjects
Animals, Mammals, Bacteria, Yersinia pestis, Plague, N-Acetylneuraminic Acid, Polysaccharides, Protein Subunits, Bacterial Toxins, Evolution, Molecular, Phylogeny, Protein Binding, Host Specificity, bacterial, cytotoxicity, evolution, host range, pathogenesis, phylogenetic, sialoglycan microarray, toxin, Vector-Borne Diseases, Biodefense, Prevention, Emerging Infectious Diseases, Infectious Diseases, Vaccine Related, 2.2 Factors relating to the physical environment, Aetiology, Infection, Chemical Sciences, Biological Sciences, Medical and Health Sciences, Biochemistry & Molecular Biology
Abstract

Many pathogenic bacteria secrete AB5 toxins that can be virulence factors. Cytotoxic A subunits are delivered to the cytosol following B subunit binding to specific host cell surface glycans. Some B subunits are not associated with A subunits, for example, YpeB of Yersinia pestis, the etiologic agent of plague. Plague cannot be eradicated because of Y. pestis' adaptability to numerous hosts. We previously showed selective binding of other B5 pentamers to a sialoglycan microarray, with sialic acid (Sia) preferences corresponding to those prominently expressed by various hosts, for example, N-acetylneuraminic acid (Neu5Ac; prominent in humans) or N-glycolylneuraminic acid (Neu5Gc; prominent in ruminant mammals and rodents). Here, we report that A subunit phylogeny evolved independently of B subunits and suggest a future B subunit nomenclature based on bacterial species names. We also found via phylogenetic analysis of B subunits, which bind Sias, that homologous molecules show poor correlation with species phylogeny. These data indicate ongoing lateral gene transfers between species, including mixing of A and B subunits. Consistent with much broader host range of Y. pestis, we show that YpeB recognizes all mammalian Sia types, except for 4-O-acetylated ones. Notably, YpeB alone causes dose-dependent cytotoxicity, which is abolished by a mutation (Y77F) eliminating Sia recognition, suggesting that cell proliferation and death are promoted via lectin-like crosslinking of cell surface sialoglycoconjugates. These findings help explain the host range of Y. pestis and could be important for pathogenesis. Overall, our data indicate ongoing rapid evolution of both host Sias and pathogen toxin-binding properties.

Published
2022

67. Reversible O‑Acetyl Migration within the Sialic Acid Side Chain and Its Influence on Protein Recognition

Author

Ji, Yang, Sasmal, Aniruddha, Li, Wanqing, Oh, Lisa, Srivastava, Saurabh, Hargett, Audra A, Wasik, Brian R, Yu, Hai, Diaz, Sandra, Choudhury, Biswa, Parrish, Colin R, Freedberg, Darón I, Wang, Lee-Ping, Varki, Ajit, and Chen, Xi

Subjects
Biological Sciences, Organic Chemistry, Chemical Sciences, Emerging Infectious Diseases, Infectious Diseases, Acetylation, Animals, Cattle, Chromatography, High Pressure Liquid, Hemagglutinins, Viral, Molecular Structure, Oxidation-Reduction, Periodic Acid, Phenylenediamines, Polysaccharides, Protein Binding, Sialic Acids, Torovirus, Viral Fusion Proteins, Biological sciences, Chemical sciences
Abstract

O-Acetylation is a common naturally occurring modification of carbohydrates and is especially widespread in sialic acids, a family of nine-carbon acidic monosaccharides. O-Acetyl migration within the exocyclic glycerol-like side chain of mono-O-acetylated sialic acid reported previously was from the C7- to C9-hydroxyl group with or without an 8-O-acetyl intermediate, which resulted in an equilibrium that favors the formation of the 9-O-acetyl sialic acid. Herein, we provide direct experimental evidence demonstrating that O-acetyl migration is bidirectional, and the rate of equilibration is influenced predominantly by the pH of the sample. While the O-acetyl group on sialic acids and sialoglycans is stable under mildly acidic conditions (pH < 5, the rate of O-acetyl migration is extremely low), reversible O-acetyl migration is observed readily at neutral pH and becomes more significant when the pH increases to slightly basic. Sialoglycan microarray studies showed that esterase-inactivated porcine torovirus hemagglutinin-esterase bound strongly to sialoglycans containing a more stable 9-N-acetylated sialic acid analog, but these compounds were less resistant to periodate oxidation treatment compared to their 9-O-acetyl counterparts. Together with prior studies, the results support the possible influence of sialic acid O-acetylation and O-acetyl migration to host-microbe interactions and potential application of the more stable synthetic N-acetyl mimics.

Published
2021

71. Dynamics of Micelle Formation

Author

Sikder, Anupama, Shah, Saurabh, Singh, Shashi Bala, Srivastava, Saurabh, Singh, Sachin Kumar, editor, Gulati, Monica, editor, Mutalik, Srinivas, editor, Dhanasekaran, Muralikrishnan, editor, and Dua, Kamal, editor

Published
2023
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