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PMID:11121397

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Citation

Kitagawa, H, Egusa, N, Tamura, JI, Kusche-Gullberg, M, Lindahl, U and Sugahara, K (2001) rib-2, a Caenorhabditis elegans homolog of the human tumor suppressor EXT genes encodes a novel alpha1,4-N-acetylglucosaminyltransferase involved in the biosynthetic initiation and elongation of heparan sulfate. J. Biol. Chem. 276:4834-8

Abstract

The proteins encoded by the EXT1, EXT2, and EXTL2 genes, members of the hereditary multiple exostoses gene family of tumor suppressors, are glycosyltransferases required for the heparan sulfate biosynthesis. Only two homologous genes, rib-1 and rib-2, of the mammalian EXT genes were identified in the Caenorhabditis elegans genome. Although heparan sulfate is found in C. elegans, the involvement of the rib-1 and rib-2 proteins in heparan sulfate biosynthesis remains unclear. In the present study, the substrate specificity of a soluble recombinant form of the rib-2 protein was determined and compared with those of the recombinant forms of the mammalian EXT1, EXT2, and EXTL2 proteins. The present findings revealed that the rib-2 protein was a unique alpha1,4-N-acetylglucosaminyltransferase involved in the biosynthetic initiation and elongation of heparan sulfate. In contrast, the findings confirmed the previous observations that both the EXT1 and EXT2 proteins were heparan sulfate copolymerases with both alpha1,4-N-acetylglucosaminyltransferase and beta1,4-glucuronyltransferase activities, which are involved only in the elongation step of the heparan sulfate chain, and that the EXTL2 protein was an alpha1,4-N-acetylglucosaminyltransferase involved only in the initiation of heparan sulfate synthesis. These findings suggest that the biosynthetic mechanism of heparan sulfate in C. elegans is distinct from that reported for the mammalian system.

Links

PubMed Online version:10.1074/jbc.C000835200

Keywords

Animals; COS Cells; Caenorhabditis elegans/enzymology; Caenorhabditis elegans Proteins; Genes, Tumor Suppressor; Helminth Proteins/genetics; Helminth Proteins/physiology; Heparitin Sulfate/biosynthesis; Membrane Proteins; N-Acetylglucosaminyltransferases/genetics; N-Acetylglucosaminyltransferases/metabolism; N-Acetylglucosaminyltransferases/physiology; N-Acetylhexosaminyltransferases/metabolism; Proteins/metabolism; Substrate Specificity; Transfection

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

CAEEL:EXT2

enables

GO:0005515: protein binding

ECO:0000353: physical interaction evidence used in manual assertion

WB:WBGene00004360

F

Seeded From UniProt

complete

CAEEL:EXT2

involved_in

GO:0015012: heparan sulfate proteoglycan biosynthetic process

ECO:0000314: direct assay evidence used in manual assertion

P

Seeded From UniProt

complete

CAEEL:EXT2

enables

GO:0042328: heparan sulfate N-acetylglucosaminyltransferase activity

ECO:0000314: direct assay evidence used in manual assertion

F

Seeded From UniProt

complete


See also

References

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