PMID: 6987220Mar 25, 1980Paper

Structure and biosynthesis of surface polymers containing polysialic acid in Escherichia coli.

The Journal of Biological Chemistry
T E Rohr, F A Troy

Abstract

Membranous sialyltransferase complexes from Escherichia coli K-235 catalyze the synthesis of surface polymers containing alpha-2,8-ketosidically linked polysialic acid. Undecaprenyl phosphate functions as an intermediate carrier of sialic acid (NeuNAc) residues between cytidine 5'-monophospho-N-acetylneuraminic acid (CMP-NeuNAc) and an endogenous acceptor (Troy, F.A., and McCloskey, M.A. (1979) J. Biol. Chem 254, 7377-7387). In vitro pulse-chase experiments now confirm that polymer elongation occurs by the addition of sialyl residues to the nonreducing termini of growing nascent chains. Sequential periodate oxidation and borohydride reduction of radiolabeled polysialic acid was used to quantitatively convert the terminal, nonreducing sialic acid to the 7-carbon analogue, 5-acetamido-3,5-dideoxy-L-arabino-2-heptulosonic acid (NeuNAc7). After complete hydrolysis of the polymers by neuraminidase, the ratio between NeuNAc and NeuNAc7 was used to determine the average degree of polymerization (D.P.). The membrane preparations used as a source of enzyme contained endogenous sialyl polymers that averaged 165 residues in length. During the first phase of in vitro synthesis, lasting about 90 min, 40 to 45 sialyl residues were transferre...Continue Reading

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