Mammalian cytidine 5′-monophosphate N-acetylneiiraminic acid synthetase: A nuclear protein with evolutionary conserved structural motifs

Anja K. Münster, Matthias Eckhardt, Barry Potvin, Martina Mühlenhoff, Pamela Stanley, Rita Gerardy-Schahn

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124 Scopus citations


Sialic acids of cell surface glycoproteins and glycolipids play a pivotal role in the structure and function of animal tissues. The pattern of cell surface sialylation is speciesand tissue-specific, is highly regulated during embryonic development, and changes with stages of differentiation. A prerequisite for the synthesis of sialylated glycoconjugates is the activated sugar-nucleotide cytidine 5′-monophosphate N-acetylneuraminic acid (CMP-Neu5Ac), which provides a substrate for Golgi sialyltransferases. Although a mammalian enzymatic activity responsible for the synthesis of CMP-Neu5Ac has been described and the enzyme has been purified to near homogeneity, sequence information is restricted to bacterial CMP-Neu5Ac synthetases. In this paper, we describe the molecular characterization, functional expression, and subcellular localization of murine CMP-Neu5Ac synthetase. Cloning was achieved by complementation of the Chinese hamster ovary lec32 mutation that causes a deficiency in CMP-Neu5Ac synthetase activity. A murine cDNA encoding a protein of 432 amino acids rescued the lec32 mutation and also caused polysialic acid to be expressed in the capsule of the CMP-Neu5Ac synthetase negative Escherichia coli mutant EV5. Three potential nuclear localization signals were found in the murine synthetase, and immunofluorescence studies confirmed predominantly nuclear localization of an N-terminally Flag-tagged molecule. Four stretches of amino acids that occur in the N-terminal region are highly conserved in bacterial CMP-Neu5Ac synthetases, providing evidence for an ancestral relationship between the sialylation pathways of bacterial and animal cells.

Original languageEnglish (US)
Pages (from-to)9140-9145
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number16
StatePublished - Aug 4 1998


  • Nuclear localization
  • Nucleotidyltransferases
  • Polysialic acid
  • Sialic acid

ASJC Scopus subject areas

  • General


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