View source for 1ltg

==THE ARG7LYS MUTANT OF HEAT-LABILE ENTEROTOXIN EXHIBITS GREAT FLEXIBILITY OF ACTIVE SITE LOOP 47-56 OF THE A SUBUNIT==
<StructureSection load='1ltg' size='340' side='right' caption='[[1ltg]], [[Resolution|resolution]] 2.40&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1ltg]] is a 7 chain structure with sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1LTG OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1LTG FirstGlance]. <br>
</td></tr><tr><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1ltg FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1ltg OCA], [http://www.rcsb.org/pdb/explore.do?structureId=1ltg RCSB], [http://www.ebi.ac.uk/pdbsum/1ltg PDBsum]</span></td></tr>
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== 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/lt/1ltg_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/chain_selection.php?pdb_ID=2ata ConSurf].
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== Publication Abstract from PubMed ==
The heat-labile enterotoxin from Escherichia coli (LT) is a member of the cholera toxin family. These and other members of the larger class of AB5 bacterial toxins act through catalyzing the ADP-ribosylation of various intracellular targets including Gs alpha. The A subunit is responsible for this covalent modification, while the B pentamer is involved in receptor recognition. We report here the crystal structure of an inactive single-site mutant of LT in which arginine 7 of the A subunit has been replaced by a lysine residue. The final model contains 103 residues for each of the five B subunits, 175 residues for the A1 subunit, and 41 residues for the A2 subunit. In this Arg7Lys structure the active site cleft within the A subunit is wider by approximately 1 A than is seen in the wild-type LT. Furthermore, a loop near the active site consisting of residues 47-56 is disordered in the Arg7Lys structure, even though the new lysine residue at position 7 assumes a position which virtually coincides with that of Arg7 in the wild-type structure. The displacement of residues 47-56 as seen in the mutant structure is proposed to be necessary for allowing NAD access to the active site of the wild-type LT. On the basis of the differences observed between the wild-type and Arg7Lys structures, we propose a model for a coordinated sequence of conformational changes required for full activation of LT upon reduction of disulfide bridge 187-199 and cleavage of the peptide loop between the two cysteines in the A subunit.(ABSTRACT TRUNCATED AT 250 WORDS)

The Arg7Lys mutant of heat-labile enterotoxin exhibits great flexibility of active site loop 47-56 of the A subunit.,van den Akker F, Merritt EA, Pizza M, Domenighini M, Rappuoli R, Hol WG Biochemistry. 1995 Sep 5;34(35):10996-1004. PMID:7669757<ref>PMID:7669757</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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== References ==
<references/>
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</StructureSection>
[[Category: Escherichia coli]]
[[Category: Akker, F Van Den.]]
[[Category: Hol, W G.J.]]
[[Category: Enterotoxin]]