Characterization and carbohydrate specificity of pradimicin S.
The pradimicin family of antibiotics is attracting attention due to its anti-infective properties and as a model for understanding the requirements for carbohydrate recognition by small molecules. Members of the pradimicin family are unique among natural products in their ability to bind sugars in a Ca(2+)-dependent manner, but the oligomerization to insoluble aggregates that occurs upon Ca(2+) binding has prevented detailed characterization of their carbohydrate specificity and biologically relevant form. Here we take advantage of the water solubility of pradimicin S (PRM-S), a sulfated glucose-containing analogue of pradimicin A (PRM-A), to show by NMR spectroscopy and analytical ultracentrifugation that at biologically relevant concentrations, PRM-S binds Ca(2+) to form a tetrameric species that selectively binds and engulfs the trisaccharide Manα1-3(Manα1-6)Man over mannose or mannobiose. In functional HIV-1 entry assays, IC(50) values of 2-4 μM for PRM-S corrrelate with the concentrations at which oligomerization occurs as well as the affinities with which PRM-S binds the HIV surface envelope glycoprotein gp120. Together these data reveal the biologically active form of PRM-S, provide an explanation for previous speculations that PRM-A may contain a second mannose binding site, and expand our understanding of the characteristics that can engender a small molecule with the ability to function as a carbohydrate receptor.
Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, United States.
Syed
S
Shahzad-ul-Hussan
Rodolfo
R
Ghirlando
Cajetan I
CI
Dogo-Isonagie
Yasuhiro
Y
Igarashi
Jan
J
Balzarini
Carole A
CA
Bewley
D018943:Anthracyclines / Q000378:metabolism / Q000494:pharmacology*; D019380:Anti-HIV Agents / Q000378:metabolism / Q000494:pharmacology*; D000890:Anti-Infective Agents / Q000378:metabolism / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015699:HIV Envelope Protein gp120 / Q000378:metabolism*; D015658:HIV Infections / Q000188:drug therapy; D015497:HIV-1 / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D008351:Mannans / Q000378:metabolism; D008358:Mannose / Q000378:metabolism; D014312:Trisaccharides / Q000737:chemistry / Q000378:metabolism*; D053586:Virus Internalization / Q000187:drug effects; D000095643:Pradimicins and Benanomicins
D018943:Anthracyclines; D019380:Anti-HIV Agents; D000890:Anti-Infective Agents; D002118:Calcium; D015699:HIV Envelope Protein gp120; D008351:Mannans; D008358:Mannose; D014312:Trisaccharides; C080896:pradimicin S; D000095643:Pradimicins and Benanomicins; C014647:mannobiose