4PHQ: Clya Cc6/264 Ox (6-303)

The alpha-pore-forming toxin Cytolysin A (ClyA) is responsible for the hemolytic phenotype of several Escherichia coli and Salmonella enterica strains. ClyA is a soluble, 34 kDa monomer that assembles into a dodecameric pore complex in the presence of membranes or detergent. The comparison of the X-ray structures of monomeric ClyA and the ClyA protomer in the pore complex revealed one of the largest conformational transitions observed so far in proteins, involving the structural rearrangement of more than half of all residues, which is consistent with the finding that conversion from the monomer to the assembly competent protomer is rate-limiting for pore assembly. Here, we introduced artificial disulfide bonds at two distinct sites into the ClyA monomer that both prevent a specific structural rearrangement required for protomer formation. Using electron microscopy and hemolytic activity assays, we show that the engineered disulfides indeed trap these ClyA variants in an assembly incompetent state. Assembly of the variants into functional pore complexes can be completely recovered by disulfide reduction. The assembly kinetics of the ClyA variants recorded with circular dichroism and fluorescence spectroscopy revealed the same mechanism of protomer formation that was observed for wild-type ClyA, proceeding via an intermediate with decreased secondary structure content.
PDB ID: 4PHQDownload
MMDB ID: 123429
PDB Deposition Date: 2014/5/6
Updated in MMDB: 2014/11
Experimental Method:
x-ray diffraction
Resolution: 1.94  Å
Source Organism:
Similar Structures:
Biological Unit for 4PHQ: monomeric; determined by author and by software (PISA)
Molecular Components in 4PHQ
Label Count Molecule
Protein (1 molecule)
Hemolysin E, Chromosomal(Gene symbol: hlyE)
Molecule annotation
Chemicals (6 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB