STRUCTURAL STUDIES ON THE POLYSACCHARIDE PORTION OF A-BAND LIPOPOLYSACCHARIDE FROM A MUTANT (AK1401) OF PSEUDOMONAS-AERUGINOSA STRAIN PAO1

AK1401 is a mutant of Pseudomonas aeruginosa strain PAO1 (serotype O5) that does not express O-antigen, but does express "A-band" lipopolysaccharide (LPS). The polysaccharide portion of the A-band LPS (A-PS) from AK1401 was found to consist mainly of D-rhamnose, with smaller amounts of 3-O-methylrhamnose, ribose, mannose, glucose, and a 3-O-methylhexose. H-1 nuclear magnetic resonance spectra of the intact A-PS indicated that the main structural feature was a repeating trisaccharide of alpha-D-rhamnose having the following structure: [-->2-alpha-D-Rhap-(1 --> 3)-alpha-D-Rhap-(1 --> 3)-alpha-D-Rhap-(1 -->]n The H-1 NMR spectrum of the repeating unit was completely assigned through the use of 2D shift-correlated and relayed coherence transfer NMR spectroscopy. The linkage positions and sequence of residues were found by nuclear Overhauser enhancement difference spectroscopy.