Affiliation:
1. Department of Cell and Molecular Biology, BMC, PO Box 596, SE 751 24, Uppsala, Sweden
Abstract
Fusidic acid (FA) is a bacteriostatic antibiotic that locks elongation factor G (EF-G) to the ribosome after GTP hydrolysis during elongation and ribosome recycling. The plasmid pUB101-encoded protein FusB causes FA resistance in clinical isolates of
Staphylococcus aureus
through an interaction with EF-G. Here, we report 1.6 and 2.3 Å crystal structures of FusB. We show that FusB is a two-domain protein lacking homology to known structures, where the N-terminal domain is a four-helix bundle and the C-terminal domain has an alpha/beta fold containing a C4 treble clef zinc finger motif and two loop regions with conserved basic residues. Using hybrid constructs between
S. aureus
EF-G that binds to FusB and
Escherichia coli
EF-G that does not, we show that the sequence determinants for FusB recognition reside in domain IV and involve the C-terminal helix of
S. aureus
EF-G. Further, using kinetic assays in a reconstituted translation system, we demonstrate that FusB can rescue FA inhibition of tRNA translocation as well as ribosome recycling. We propose that FusB rescues
S. aureus
from FA inhibition by preventing formation or facilitating dissociation of the FA-locked EF-G–ribosome complex.
Subject
General Biochemistry, Genetics and Molecular Biology,Immunology,General Neuroscience
Cited by
23 articles.
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