MOLECULAR-CLONING, SEQUENCE-ANALYSIS, AND FUNCTIONAL-CHARACTERIZATION OF THE LIPOPOLYSACCHARIDE BIOSYNTHETIC GENE KDTA ENCODING 3-DEOXY-ALPHA-D-MANNO-OCTULOSONIC ACID TRANSFERASE OF CHLAMYDIA-PNEUMONIAE STRAIN TW-183

The gene kdtA of Chlamydia pneumoniae strain TW-183, encoding the enzyme 3-deoxy-alpha-D-manno-octulosonic acid (Kdo) transferase of lipopolysaccharide biosynthesis, was cloned and sequenced. A single open reading frame of 1314 bp was identified, the deduced amino acid sequence of which revealed 69% similarity and 43% identity with KdtA of Chlamydia trachomatis and Chlamydia psittaci. The gene was expressed in the Gram-positive host Corynebacterium glutamicum and the primary gene product was characterized as a multifunctional glycosyltransferase. Cell-free extracts generated in vitro the genus-specific epitope of Chlamydia composed of the trisaccharide alpha Kdo(2-8)alpha Kdo(2-4)alpha Kdo, The results show that a single polypeptide affords three different glycosidic bonds, which is in contradiction to the dogma of glycobiology: 'one enzyme - one glycosidic bond'.