Identification of a Putative Sordarin Binding Site in
Candida albicans Elongation Factor 2 by Photoaffinity
Labeling*
Juan Manuel
Domínguez
and
J. Julio
Martín
From the Research Department, GlaxoSmithKline S. A. PTM,
C/Severo Ochoa 2, 28760 Tres Cantos, Madrid, Spain
Candida albicans EF-2 binds sordarin
to a single class of binding sites with Kd = 1.26 µM. Equimolar mixtures of EF-2 and ribosomes, in the
presence of a non-hydrolyzable GTP analog, reveal two classes of high
affinity sordarin binding sites with Kd = 0.7 and
41.5 nM, probably due to the existence of two ribosome
populations. Photoaffinity labeling of C. albicans EF-2 in
the absence of ribosomes has been performed with
[14C]GM258383, a photoactivatable sordarin derivative.
Labeling is saturable and can be considered specific, because it can be
prevented with another sordarin analog. The fragment
Gln224-Lys232 has been identified as
the modified peptide within the EF-2 sequence, Lys228 being
the residue to which the photoprobe was linked. This fragment is
included within the G"-subdomain of EF-2. These results are discussed
in the light of the high sordarin specificity toward fungal systems.
*
The costs of publication of this
article were defrayed in part by the
payment of page charges. The article
must therefore be hereby marked
"advertisement" in
accordance with 18 U.S.C. Section
1734 solely to indicate this fact.
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