Involved in lipopolysaccharide (LPS) biosynthesis. Catalyzes the transfer of a single 3-deoxy-D-manno-octulosonate (Kdo) residue from CMP-Kdo to lipid IV(A), the tetraacyldisaccharide-1,4'-bisphosphate precursor of lipid A. Is strictly monofunctional, i.e. is capable of adding only a single Kdo residue to the acceptor lipid. CMP-3-deoxy-beta-D-manno-octulosonate + lipid IVA (E. coli) = alpha-Kdo-(2->6)-lipid IVA + CMP + H(+) Highly thermostable. Does not lose activity after 16 hours at 70 or 80 degrees Celsius, but incubation of the enzyme at 90 and 99 degrees Celsius for 1 hour results in gradual loss of activity. Bacterial outer membrane biogenesis; LPS core biosynthesis. Can form homodimer, homotrimer and homotetramer. Belongs to the glycosyltransferase group 1 family. Glycosyltransferase 30 subfamily.