1S5C

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

Summary for 1S5C

• Entry DOI: 10.2210/pdb1s5c/pdb
• Related: 1LTA 1LTG 1LTS 1XTC
• Descriptor: Cholera enterotoxin, A chain, cholera enterotoxin B-subunit, SODIUM ION, ... (4 entities in total)
• Functional Keywords: cholera toxin, heat-labile enterotoxin, adp ribose transferases, ab5 toxins, transferase, toxin
• Biological source: Vibrio cholerae; More
• Cellular location: Secreted: P01556
• Total number of polymer chains: 6
• Total formula weight: 85292.20

Authors

O'Neal, C.J.,Amaya, E.I.,Jobling, M.G.,Holmes, R.K.,Hol, W.G. (deposition date: 2004-01-20, release date: 2004-04-06, Last modification date: 2023-08-23)

Primary citation

O'Neal, C.J.,Amaya, E.I.,Jobling, M.G.,Holmes, R.K.,Hol, W.G.
Crystal structures of an intrinsically active cholera toxin mutant yield insight into the toxin activation mechanism
Biochemistry, 43:3772-3782, 2004

PubMed Abstract: 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.

PubMed: 15049684
DOI: 10.1021/bi0360152

Experimental method

X-RAY DIFFRACTION (2.5 Å)