Structure and epitope specificity of the O-specific polysaccharide of Proteus penneri strain 12 (ATCC 33519) containing the amide of D-galacturonic acid with L-threonine.

O-specific polysaccharide was isolated from Proteus penneri strain 12 (ATCC 33519) lipopolysaccharide (LPS) and studied using NMR spectroscopy, including selective spin-decoupling, one-dimensional NOE, two-dimensional homonuclear correlation spectroscopy, 13C,1H heteronuclear correlation spectroscopy and chemical methods (O-deacetylation, Smith degradation, partial acid hydrolysis followed by borohydride reduction and methylation). The amide of D-galacturonic acid with L-threonine [D-GalA(L-Thr)] was identified as a constituent of the polysaccharide and the following structure of the tetrasaccharide repeating unit was established: [formula: see text] where the degree of O-acetylation at either position varies over 20-40%. Serological study with LPS, its degradation products and related synthetic glycoconjugates (2-acrylamidoethyl glycosides of amides of alpha-D-GalA with L-amino acids copolymerised with acrylamide) showed that D-GalA(L-Thr) plays an important role in manifesting the serological specificity of the P. penneri 12 O-antigen. Serological cross reactions between LPSs of P. penneri 12 and Proteus mirabilis S1959, R14/S1959 (transient-like form), O23 and O28 are discussed.