Characterisation of a candidate sialidase gene in the human major histocompatability complex

CM Milner, SV Smith, MB Carillo, Garry Lindsay Taylor, RD Campbell

Research output: Contribution to journalArticlepeer-review

107 Citations (Scopus)

Abstract

Mammalian sialidases are important in modulating the sialic acid content of cell-surface and intracellular glycoproteins. However, the full extent of this enzyme family and the physical and biochemical properties of its individual members are unclear. We have identified a novel gene, G9, in the human major histocompatibility complex (MHC), that encodes a 415-amino acid protein sharing 21-28% sequence identity with the bacterial sialidases and containing three copies of the Asp-block motif characteristic of these enzymes. The level of sequence identity between human G9 and a cytosolic sialidase identified in rat and hamster (28-29%) is much less than would be expected for analogous proteins in these species, suggesting that G9 is distinct from the cytosolic enzyme. Expression of G9 in insect cells has confirmed that it encodes a sialidase, which shows optimal activity at pH 4.6, but appears to have limited substrate specificity. The G9 protein carries an N-terminal signal sequence and immunofluorescence staining of COS7 cells expressing recombinant G9 shows localization of this sialidase exclusively to the endoplasmic reticulum. The location of the G9 gene, within the human MHC, corresponds to that of the murine Neu-1 locus, suggesting that these are analogous genes. One of the functions attributed to Neu-1 is the up-regulation of sialidase activity during T cell activation.

Original languageEnglish
Pages (from-to)4549-4558
Number of pages10
JournalJournal of Biological Chemistry
Volume272
Publication statusPublished - 14 Feb 1997

Keywords

  • HUMAN NEURAMINIDASE DEFICIENCY
  • VIBRIO-CHOLERAE NEURAMINIDASE
  • CLASS-III REGION
  • ENDOPLASMIC-RETICULUM
  • MEMBRANE-PROTEINS
  • BACTERIAL SIALIDASES
  • CYTOSOLIC SIALIDASE
  • BETA-GALACTOSIDASE
  • MOUSE H-2-COMPLEX
  • CRYSTAL-STRUCTURE

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