1tw5: Difference between revisions
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{{STRUCTURE_1tw5| PDB=1tw5 | SCENE= }} | |||
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'''beta1,4-galactosyltransferase mutant M344H-Gal-T1 in complex with Chitobiose''' | '''beta1,4-galactosyltransferase mutant M344H-Gal-T1 in complex with Chitobiose''' | ||
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[[Category: Qasba, P K.]] | [[Category: Qasba, P K.]] | ||
[[Category: Ramakrishnan, B.]] | [[Category: Ramakrishnan, B.]] | ||
[[Category: | [[Category: Chitobiose binding]] | ||
[[Category: | [[Category: Closed conformation]] | ||
[[Category: | [[Category: Met344his mutation]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 10:26:39 2008'' | |||
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Revision as of 10:26, 3 May 2008
beta1,4-galactosyltransferase mutant M344H-Gal-T1 in complex with Chitobiose
OverviewOverview
Beta-1,4-galactosyltransferase (beta4Gal-T1) in the presence of manganese ion transfers galactose from UDP-galactose (UDP-Gal) to N-acetylglucosamine (GlcNAc) that is either free or linked to an oligosaccharide. Crystallographic studies on bovine beta4Gal-T1 have shown that the primary metal binding site is located in the hinge region of a long flexible loop, which upon Mn(2+) and UDP-Gal binding changes from an open to a closed conformation. This conformational change creates an oligosaccharide binding site in the enzyme. Neither UDP nor UDP analogues efficiently induce these conformational changes in the wild-type enzyme, thereby restricting the structural analysis of the acceptor binding site. The binding of Mn(2+) involves an uncommon coordination to the Sdelta atom of Met344; when it is mutated to His, the mutant M344H, in the presence of Mn(2+) and UDP-hexanolamine, readily changes to a closed conformation, facilitating the structural analysis of the enzyme bound with an oligosaccharide acceptor. Although the mutant M344H loses 98% of its Mn(2+)-dependent activity, it exhibits 25% of its activity in the presence of Mg(2+). The crystal structures of M344H-Gal-T1 in complex with either UDP-Gal.Mn(2+) or UDP-Gal.Mg(2+), determined at 2.3 A resolution, show that the mutant enzyme in these complexes is in a closed conformation, and the coordination stereochemistry of Mg(2+) is quite similar to that of Mn(2+). Although either Mn(2+) or Mg(2+), together with UDP-Gal, binds and changes the conformation of the M344H mutant to the closed one, it is the Mg(2+) complex that engages efficiently in catalyses. Thus, this property enabled us to crystallize the M344H mutant for the first time with the acceptor substrate chitobiose in the presence of UDP-hexanolamine and Mn(2+). The crystal structure determined at 2.3 A resolution reveals that the GlcNAc residue at the nonreducing end of chitobiose makes extensive hydrophobic interactions with the highly conserved Tyr286 residue.
About this StructureAbout this Structure
1TW5 is a Single protein structure of sequence from Bos taurus. Full crystallographic information is available from OCA.
ReferenceReference
Effect of the Met344His mutation on the conformational dynamics of bovine beta-1,4-galactosyltransferase: crystal structure of the Met344His mutant in complex with chitobiose., Ramakrishnan B, Boeggeman E, Qasba PK, Biochemistry. 2004 Oct 5;43(39):12513-22. PMID:15449940 Page seeded by OCA on Sat May 3 10:26:39 2008