Probing the Ca(2+)-assisted π-π interaction during Ca(2+)-dependent protein folding.
Protein folding is governed by a balance of non-covalent interactions, of which cation-π and π-π play important roles. Theoretical calculations revealed a strong cooperativity between cation-π involving alkali and alkaline earth metal ions and π-π interactions, but however, no experimental evidence was provided in this regard. Here, we characterized a Ca(2+)-binding self-processing module (SPM), which mediates a highly-specific Ca(2+)-dependent autocatalytic processing of iron-regulated protein FrpC secreted by the pathogenic Gram-negative bacterium Neisseria meningitidis. The SPM undergoes a Ca(2+)-induced transition from an intrinsically unstructured conformation to the compact protein fold that is ultimately stabilized by the π-π interaction between two unique tryptophan residues arranged in the T-shaped orientation. Moreover, the pair of tryptophans is located in a close vicinity of a calcium-binding site, suggesting the involvement of a Ca(2+)-assisted π-π interaction in the stabilization of the tertiary structure of the SPM. This makes the SPM an excellent model for the investigation of the Ca(2+)-assisted π-π interaction during Ca(2+)-induced protein folding.
Laboratory of Molecular Biology of Bacterial Pathogens, Institute of Microbiology of the ASCR, v.v.i., Videnska 1083, 14200 Prague, Czech Republic. bumba@biomed.cas.cz.
Petra
P
Matyska Liskova
Radovan
R
Fiser
Pavel
P
Macek
Josef
J
Chmelik
Jan
J
Sykora
Lucie
L
Bednarova
Ivo
I
Konopasek
Ladislav
L
Bumba
D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology*; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation / Q000187:drug effects; D017510:Protein Folding / Q000187:drug effects*; D058767:Protein Unfolding / Q000187:drug effects
D001426:Bacterial Proteins; D008565:Membrane Proteins; C083530:frpC protein, Neisseria meningitidis; D002118:Calcium