Characterization of the physiological substrate for lipopolysaccharide heptosyltransferases I and II

Abstract

L- Glycero-D- manno-heptopyranose is a characteristic compound of many lipopolysaccharide (LPS) core structures of Gram-negative bacteria. In Escherichia coli two heptosyltransferases, namely WaaC and WaaF, are known to transfer L- glycero-D- manno-heptopyranose to Re-LPS and Rd 2-LPS, respectively. It had been proposed that both reactions involve ADPL- glycero-D- manno-heptose as a sugar donor; however, the structure of this nucleotide sugar had never been completely elucidated. In the present study, ADPL- glycero-D- manno-heptose was isolated from a heptosyltransferase-deficient E. coli mutant, and its structure was determined by nuclear magnetic resonance spectroscopy and matrix-assisted laser-desorption/ionization time-of-flight mass spectrometry as ADPL- glycero-β-D- manno-heptopyranose. This compound represented the sole constituent of the bacterial extract that was accepted as a sugar donor by heptosyltransferases I and II in vitro .