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1nkh

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[[Image:1nkh.gif|left|200px]]
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[[Image:1nkh.png|left|200px]]
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==Overview==
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{{ABSTRACT_11419947}}
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The lactose synthase (LS) enzyme is a 1:1 complex of a catalytic component, beta1,4-galactosyltransferse (beta4Gal-T1) and a regulatory component, alpha-lactalbumin (LA), a mammary gland-specific protein. LA promotes the binding of glucose (Glc) to beta4Gal-T1, thereby altering its sugar acceptor specificity from N-acetylglucosamine (GlcNAc) to glucose, which enables LS to synthesize lactose, the major carbohydrate component of milk. The crystal structures of LS bound with various substrates were solved at 2 A resolution. These structures reveal that upon substrate binding to beta4Gal-T1, a large conformational change occurs in the region comprising residues 345 to 365. This repositions His347 in such a way that it can participate in the coordination of a metal ion, and creates a sugar and LA-binding site. At the sugar-acceptor binding site, a hydrophobic N-acetyl group-binding pocket is found, formed by residues Arg359, Phe360 and Ile363. In the Glc-bound structure, this hydrophobic pocket is absent. For the binding of Glc to LS, a reorientation of the Arg359 side-chain occurs, which blocks the hydrophobic pocket and maximizes the interactions with the Glc molecule. Thus, the role of LA is to hold Glc by hydrogen bonding with the O-1 hydroxyl group in the acceptor-binding site on beta4Gal-T1, while the N-acetyl group-binding pocket in beta4Gal-T1 adjusts to maximize the interactions with the Glc molecule. This study provides details of a structural basis for the partially ordered kinetic mechanism proposed for lactose synthase.
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==About this Structure==
==About this Structure==
1NKH is a [[Protein complex]] structure of sequences from [http://en.wikipedia.org/wiki/Bos_taurus Bos taurus] and [http://en.wikipedia.org/wiki/Mus_musculus Mus musculus]. This structure supersedes the now removed PDB entry [http://oca.weizmann.ac.il/oca-bin/send-pdb?obs=1&id=1j8x 1j8x]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1NKH OCA].
1NKH is a [[Protein complex]] structure of sequences from [http://en.wikipedia.org/wiki/Bos_taurus Bos taurus] and [http://en.wikipedia.org/wiki/Mus_musculus Mus musculus]. This structure supersedes the now removed PDB entry [http://oca.weizmann.ac.il/oca-bin/send-pdb?obs=1&id=1j8x 1j8x]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1NKH OCA].
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==Reference==
 
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Crystal structure of lactose synthase reveals a large conformational change in its catalytic component, the beta1,4-galactosyltransferase-I., Ramakrishnan B, Qasba PK, J Mol Biol. 2001 Jun 29;310(1):205-18. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/11419947 11419947]
 
[[Category: Bos taurus]]
[[Category: Bos taurus]]
[[Category: Mus musculus]]
[[Category: Mus musculus]]
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[[Category: Lactose synthease]]
[[Category: Lactose synthease]]
[[Category: Udp and mn binding]]
[[Category: Udp and mn binding]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 02:38:23 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Wed Jun 25 19:18:41 2008''

Revision as of 16:18, 25 June 2008

Image:1nkh.png

Template:STRUCTURE 1nkh

Crystal structure of Lactose synthase complex with UDP and Manganese


Template:ABSTRACT 11419947

About this Structure

1NKH is a Protein complex structure of sequences from Bos taurus and Mus musculus. This structure supersedes the now removed PDB entry 1j8x. Full crystallographic information is available from OCA.

Page seeded by OCA on Wed Jun 25 19:18:41 2008

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