Format

Send to

Choose Destination
See comment in PubMed Commons below
Biochemistry. 1998 Feb 24;37(8):2378-83.

Streptolysin O: a proposed model of allosteric interaction between a pore-forming protein and its target lipid bilayer.

Author information

1
Institute of Medical Microbiology, University of Mainz, Augustusplatz, D55101 Germany.

Abstract

Streptolysin O, a polypeptide of 571 amino acids, belongs to the family of thiol-activated toxins that permeabilize animal cell membranes. The protein binds as a monomer to membrane cholesterol. Binding involves a conserved region close to the C-terminus and triggers subsequent polymerization into large arc- and ring-shaped structures surrounding pores of up to 30 nm. Besides the C-terminus, a distantly located region spanning residues 213-305 is involved in oligomerization and in membrane insertion. Here, we searched for conformational effects of monomer binding to the latter functionally important region. To this end, single cysteine substitution mutants were produced and derivatized with the polarity-sensitive fluorophore acrylodan. Fluorimetric measurements revealed that binding of the monomer to membranes is accompanied by distinct environmental changes at amino acid residues 218, 248, 266, and 277. Conspicuously, the environment of residues 218 and 266 became more hydrophilic, suggesting movement of these residues out of hydrophobic protein pockets. Upon oligomerization, further alterations in all side-chain environments were observed. The membrane-bound monomer thus differs in conformation from both the monomer in solution and the subunit of the oligomer. The putative binding site of the molecule is linked to remote domains involved in oligomerization and membrane insertion in an apparently allosteric fashion. It is proposed that allostery is responsible for restricting oligomerization to the membrane-bound state of the toxin.

PMID:
9485385
DOI:
10.1021/bi9720890
[Indexed for MEDLINE]
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for American Chemical Society
    Loading ...
    Support Center