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			PubMed Journals: Biochim Biophys Acta

  Source:		PMID: 11690653


    		Biochim Biophys Acta. 2001 Oct 18;1549(2):161-73.
     
			Delineation of the minimal catalytic domain
			of human Galbeta1-3GalNAc alpha2,3-sialyltransferase
			(hST3Gal I).

			Vallejo-Ruiz V(1), Haque R, Mir AM, Schwientek
			T, Mandel U, Cacan R, Delannoy P, Harduin-Lepers
			A.

			Author Information
			(1) Unité de Glycobiologie Structurale et
			Fonctionnelle, Université des Sciences et
			Technologies de Lille, Villeneuve d'Ascq,
			France.

			The CMP-Neu5Ac:Galbeta1-3GalNAc
			alpha2,3-sialyltransferase (ST3Gal I, EC
			2.4.99.4) is a Golgi membrane-bound type
			II glycoprotein that catalyses the transfer
			of sialic acid residues to Galbeta1-3GalNAc
			disaccharide structures found on O-glycans
			and glycolipids. In order to gain further
			insight into the structure/function of this
			sialyltransferase, we studied protein expression,
			N-glycan processing and enzymatic activity
			upon transient expression in the COS-7 cell
			line of various constructs deleted in the
			N-terminal portion of the protein sequence. The expressed
			soluble polypeptides were detected within
			the cell and in the cell culture media using
			a specific hST3Gal I monoclonal antibody.
			The soluble forms of the protein consisting
			of amino acids 26-340 (hST3-Delta25) and
			57-340 (hST3-Delta56) were efficiently secreted
			and active. In contrast, further deletion
			of the N-terminal region leading to hST3-Delta76
			and hST3-Delta105 gave also rise to various
			polypeptides that were not active within
			the transfected cells and not secreted in
			the cell culture media. The kinetic parameters
			of the active secreted forms were determined
			and shown to be in close agreement with
			those of the recombinant enzyme already
			described (H. Kitagawa, J.C. Paulson, J.
			Biol. Chem. 269 (1994)). In addition, the
			present study demonstrates that the recombinant
			hST3Gal I polypeptides transiently expressed
			in COS-7 cells are glycosylated with complex
			and high mannose type glycans on each of
			the five potential N-glycosylation sites.

			PMID: 11690653 [Indexed for MEDLINE]

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