View source for 1alc


==REFINED STRUCTURE OF BABOON ALPHA-LACTALBUMIN AT 1.7 ANGSTROMS RESOLUTION. COMPARISON WITH C-TYPE LYSOZYME==
<StructureSection load='1alc' size='340' side='right'caption='[[1alc]], [[Resolution|resolution]] 1.70&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1alc]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Papio_cynocephalus Papio cynocephalus]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1ALC OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1ALC FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 1.7&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CA:CALCIUM+ION'>CA</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=1alc FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1alc OCA], [https://pdbe.org/1alc PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1alc RCSB], [https://www.ebi.ac.uk/pdbsum/1alc PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1alc ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/LALBA_PAPCY LALBA_PAPCY] Regulatory subunit of lactose synthase, changes the substrate specificity of galactosyltransferase in the mammary gland making glucose a good acceptor substrate for this enzyme. This enables LS to synthesize lactose, the major carbohydrate component of milk. In other tissues, galactosyltransferase transfers galactose onto the N-acetylglucosamine of the oligosaccharide chains in glycoproteins.
== Evolutionary Conservation ==
[[Image:Consurf_key_small.gif|200px|right]]
Check<jmol>
  <jmolCheckbox>
    <scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/al/1alc_consurf.spt"</scriptWhenChecked>
    <scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview01.spt</scriptWhenUnchecked>
    <text>to colour the structure by Evolutionary Conservation</text>
  </jmolCheckbox>
</jmol>, as determined by [http://consurfdb.tau.ac.il/ ConSurfDB]. You may read the [[Conservation%2C_Evolutionary|explanation]] of the method and the full data available from [http://bental.tau.ac.il/new_ConSurfDB/main_output.php?pdb_ID=1alc ConSurf].
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== Publication Abstract from PubMed ==
The solution of the structure of alpha-lactalbumin from baboon milk (Papio cynocephalus) at 4.5 A resolution using the isomorphous replacement method has been reported previously. Initial refinement on the basis of these low-resolution studies was not successful because of the poor isomorphism of the best heavy-atom derivative. Because of the striking similarity between the structure of lysozyme and alpha-lactalbumin, a more cautious molecular replacement approach was tried to refine the model. Using hen egg-white lysozyme as the starting model, preliminary refinement was performed using heavily constrained least-squares minimization in reciprocal space. The model was further refined using stereochemical restraints at 1.7 A resolution to a conventional crystallographic residual of 0.22 for 1141 protein atoms. In the final model, the root-mean-square deviation from ideality for bond distances is 0.015 A, and for angle distances it is 0.027 A. The refinement was carried out using the human alpha-lactalbumin sequence and "omit maps" calculated during the course of refinement indicated eight possible sequence changes in the baboon alpha-lactalbumin X-ray sequence. During the refinement, a tightly bound calcium ion and 150 water molecules, of which four are internal, have been located. Some of the water molecules were modelled for disordered side-chains. The co-ordination around the calcium is a slightly distorted pentagonal bipyramid. The Ca-O distances vary from 2.2 A to 2.6 A, representing a tight calcium-binding loop in the structure. The calcium-binding fold only superficially resembles the "EF-hand" and presumably has no evolutionary relationship with other EF-hand structures. The overall structure of alpha-lactalbumin is very similar to that of lysozyme. All large deviations occur in the loops where all sequence deletions and insertions are found. The C terminus appears to be rather flexible in alpha-lactalbumin compared to lysozyme. The experimental evidence supports the earlier predictions for the alpha-lactalbumin structure that were based upon the assumption that alpha-lactalbumin and lysozyme have similar three-dimensional structures, with minimal deletions and insertions. A detailed comparison of the two structures shows striking features as well as throwing some light on the evolution of these two proteins from a common precursor.

Refined structure of baboon alpha-lactalbumin at 1.7 A resolution. Comparison with C-type lysozyme.,Acharya KR, Stuart DI, Walker NP, Lewis M, Phillips DC J Mol Biol. 1989 Jul 5;208(1):99-127. PMID:2769757<ref>PMID:2769757</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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==See Also==
*[[Alpha-lactalbumin 3D structures|Alpha-lactalbumin 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: Papio cynocephalus]]
[[Category: Acharya KR]]
[[Category: Phillips DC]]
[[Category: Stuart DI]]