1s5c: Difference between revisions

Revision as of 15:58, 21 February 2008

Cholera holotoxin with an A-subunit Y30S mutation, Crystal form 1

OverviewOverview

Cholera toxin (CT) is a heterohexameric bacterial protein toxin belonging to a larger family of A/B ADP-ribosylating toxins. Each of these toxins undergoes limited proteolysis and/or disulfide bond reduction to form the enzymatically active toxic fragment. Nicking and reduction render both CT and the closely related heat-labile enterotoxin from Escherichia coli (LT) unstable in solution, thus far preventing a full structural understanding of the conformational changes resulting from toxin activation. We present the first structural glimpse of an active CT in structures from three crystal forms of a single-site A-subunit CT variant, Y30S, which requires no activational modifications for full activity. We also redetermined the structure of the wild-type, proenzyme CT from two crystal forms, both of which exhibit (i) better geometry and (ii) a different A2 "tail" conformation than the previously determined structure [Zhang et al. (1995) J. Mol. Biol. 251, 563-573]. Differences between wild-type CT and active CTY30S are observed in A-subunit loop regions that had been previously implicated in activation by analysis of the structure of an LT A-subunit R7K variant [van den Akker et al. (1995) Biochemistry 34, 10996-11004]. The 25-36 activation loop is disordered in CTY30S, while the 47-56 active site loop displays varying degrees of order in the three CTY30S structures, suggesting that disorder in the activation loop predisposes the active site loop to a greater degree of flexibility than that found in unactivated wild-type CT. On the basis of these six new views of the CT holotoxin, we propose a model for how the activational modifications experienced by wild-type CT are communicated to the active site.

About this StructureAbout this Structure

1S5C is a Protein complex structure of sequences from Vibrio cholerae with as ligand. Active as NAD(+)--diphthamide ADP-ribosyltransferase, with EC number 2.4.2.36 Full crystallographic information is available from OCA.

ReferenceReference

Crystal structures of an intrinsically active cholera toxin mutant yield insight into the toxin activation mechanism., O'Neal CJ, Amaya EI, Jobling MG, Holmes RK, Hol WG, Biochemistry. 2004 Apr 6;43(13):3772-82. PMID:15049684

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-[[Image:1s5c.jpg|left|200px]]<br /><applet load="1s5c" size="450" color="white" frame="true" align="right" spinBox="true"
+[[Image:1s5c.jpg|left|200px]]<br /><applet load="1s5c" size="350" color="white" frame="true" align="right" spinBox="true"
 caption="1s5c, resolution 2.50&Aring;" />
 '''Cholera holotoxin with an A-subunit Y30S mutation, Crystal form 1'''<br />
 ==Overview==
-Cholera toxin (CT) is a heterohexameric bacterial protein toxin belonging, to a larger family of A/B ADP-ribosylating toxins. Each of these toxins, undergoes limited proteolysis and/or disulfide bond reduction to form the, enzymatically active toxic fragment. Nicking and reduction render both CT, and the closely related heat-labile enterotoxin from Escherichia coli (LT), unstable in solution, thus far preventing a full structural understanding, of the conformational changes resulting from toxin activation. We present, the first structural glimpse of an active CT in structures from three, crystal forms of a single-site A-subunit CT variant, Y30S, which requires, no activational modifications for full activity. We also redetermined the, structure of the wild-type, proenzyme CT from two crystal forms, both of, which exhibit (i) better geometry and (ii) a different A2 "tail", conformation than the previously determined structure [Zhang et al. (1995), J. Mol. Biol. 251, 563-573]. Differences between wild-type CT and active, CTY30S are observed in A-subunit loop regions that had been previously, implicated in activation by analysis of the structure of an LT A-subunit, R7K variant [van den Akker et al. (1995) Biochemistry 34, 10996-11004]., The 25-36 activation loop is disordered in CTY30S, while the 47-56 active, site loop displays varying degrees of order in the three CTY30S, structures, suggesting that disorder in the activation loop predisposes, the active site loop to a greater degree of flexibility than that found in, unactivated wild-type CT. On the basis of these six new views of the CT, holotoxin, we propose a model for how the activational modifications, experienced by wild-type CT are communicated to the active site.
+Cholera toxin (CT) is a heterohexameric bacterial protein toxin belonging to a larger family of A/B ADP-ribosylating toxins. Each of these toxins undergoes limited proteolysis and/or disulfide bond reduction to form the enzymatically active toxic fragment. Nicking and reduction render both CT and the closely related heat-labile enterotoxin from Escherichia coli (LT) unstable in solution, thus far preventing a full structural understanding of the conformational changes resulting from toxin activation. We present the first structural glimpse of an active CT in structures from three crystal forms of a single-site A-subunit CT variant, Y30S, which requires no activational modifications for full activity. We also redetermined the structure of the wild-type, proenzyme CT from two crystal forms, both of which exhibit (i) better geometry and (ii) a different A2 "tail" conformation than the previously determined structure [Zhang et al. (1995) J. Mol. Biol. 251, 563-573]. Differences between wild-type CT and active CTY30S are observed in A-subunit loop regions that had been previously implicated in activation by analysis of the structure of an LT A-subunit R7K variant [van den Akker et al. (1995) Biochemistry 34, 10996-11004]. The 25-36 activation loop is disordered in CTY30S, while the 47-56 active site loop displays varying degrees of order in the three CTY30S structures, suggesting that disorder in the activation loop predisposes the active site loop to a greater degree of flexibility than that found in unactivated wild-type CT. On the basis of these six new views of the CT holotoxin, we propose a model for how the activational modifications experienced by wild-type CT are communicated to the active site.
 ==About this Structure==
-S5C is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Vibrio_cholerae Vibrio cholerae] with NA as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/NAD(+)--diphthamide_ADP-ribosyltransferase NAD(+)--diphthamide ADP-ribosyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.4.2.36 2.4.2.36] Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1S5C OCA].
+S5C is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Vibrio_cholerae Vibrio cholerae] with <scene name='pdbligand=NA:'>NA</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/NAD(+)--diphthamide_ADP-ribosyltransferase NAD(+)--diphthamide ADP-ribosyltransferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.4.2.36 2.4.2.36] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1S5C OCA].
 ==Reference==
@@ Line 14: / Line 14: @@
 [[Category: Protein complex]]
 [[Category: Vibrio cholerae]]
-[[Category: Amaya, E.I.]]
+[[Category: Amaya, E I.]]
-[[Category: Hol, W.G.]]
+[[Category: Hol, W G.]]
-[[Category: Holmes, R.K.]]
+[[Category: Holmes, R K.]]
-[[Category: Jobling, M.G.]]
+[[Category: Jobling, M G.]]
-[[Category: Neal, C.J.O.]]
+[[Category: Neal, C J.O.]]
 [[Category: NA]]
 [[Category: ab5 toxins]]
@@ Line 25: / Line 25: @@
 [[Category: heat-labile enterotoxin]]
-''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Wed Nov 21 02:07:08 2007''
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