Domain swap of NmB PST and NmC PST. Chimeras were constructed with nucleotides 1 to 439 of synD, 440 to 1479 of synE (pWV250), 1 to 322 of synD, and 323 to 1479 of synE (pWV245) as described in Materials and Methods. The chimeric enzymes were expressed and assayed, and the linkages of their polysialic acid products were determined by the sensitivity of the enzymatic reaction products to the α-2,8-NeuNAc-specific endoneuraminidase as described in Materials and Methods.