Open AccessBinding of adenine to Stx2, the protein toxin from Escherichia coli O157:H7
Author(s) -
Cherney Maia M.,
Marcato Paola,
Mulvey George L.,
Armstrong Glen D.,
Fraser Marie E.,
James Michael N. G.
Publication year - 2006
Publication title -
acta crystallographica section f
Language(s) - English
Resource type - Journals
ISSN - 1744-3091
DOI - 10.1107/s1744309106021968
Subject(s) - protein subunit , chemistry , escherichia coli , adenosine , active site , toxin , biochemistry , shiga toxin , stereochemistry , enzyme , gene
Stx2 is a protein toxin whose catalytic subunit acts as an N ‐glycosidase to depurinate a specific adenine base from 28S rRNA. In the holotoxin, the catalytic portion, A 1, is linked to the rest of the A subunit, A 2, and A 2 interacts with the pentameric ring formed by the five B subunits. In order to test whether the holotoxin is active as an N ‐glycosidase, Stx2 was crystallized in the presence of adenosine and adenine. The crystals diffracted to ∼1.8 Å and showed clear electron density for adenine in the active site. Adenosine had been cleaved, proving that Stx2 is an active N ‐glycosidase. While the holotoxin is active against small substrates, it would be expected that the B subunits would interfere with the binding of the 28S rRNA.