Differential Effects of Thiopeptide and Orthosomycin Antibiotics on Translational GTPases

SummaryThe ribosome is a major target in the bacterial cell for antibiotics. Here, we dissect the effects that the thiopeptide antibiotics thiostrepton (ThS) and micrococcin (MiC) as well as the orthosomycin antibiotic evernimicin (Evn) have on translational GTPases. We demonstrate that, like ThS, MiC is a translocation inhibitor, and that the activation by MiC of the ribosome-dependent GTPase activity of EF-G is dependent on the presence of the ribosomal proteins L7/L12 as well as the G′ subdomain of EF-G. In contrast, Evn does not inhibit translocation but is a potent inhibitor of back-translocation as well as IF2-dependent 70S-initiation complex formation. Collectively, these results shed insight not only into fundamental aspects of translation but also into the unappreciated specificities of these classes of translational inhibitors

Ribosomal proteins : role in ribosomal functions

The assignment of specific ribosomal functions to individual ribosomal proteins is difficult due to the enormous cooperativity of the ribosome; however, important roles for distinct ribosomal proteins are becoming evident. Although ribosomal ribonucleic acid (rRNA) has the major claim to certain aspects of ribosome function, such as decoding and peptidyltransferase activity, there are also protein-dominated functional hot-spots on the ribosome such as the messenger RNA (mRNA) entry pore, the translation factor-binding site and the exit of the ribosomal tunnel. The latter is binding site for both chaperones and complexes associated with protein transport through membranes. Furthermore, the contribution of ribosomal proteins is essential for the assembly and optimal functioning of the ribosome

Structure of the N-terminal domain of the FOP (FGFR1OP) protein and implications for its dimerization and centrosomal localization

The fibroblast growth factor receptor 1 (FGFR1) oncogene partner, FOP, is a centrosomal protein that is involved in the anchoring of microtubules (MTS) to subcellular structures. The protein was originally discovered as a fusion partner with FGFR1 in oncoproteins that give rise to stem cell myeloproliferative disorders. A subsequent proteomics screen identified FOP as a component of the centrosome. FOP contains a Lis-homology (LisH) motif found in more than 100 eukaryotic proteins. LisH motifs are believed to be involved in microtubule dynamics and organization, cell migration, and chromosome segregation; several of them are associated with genetic diseases. We report here a 1.6A resolution crystal structure of the N-terminal dimerization domain of FOP. The structure comprises an alpha-helical bundle composed of two antiparallel chains, each of them having five alpha-helices. The central part of the dimer contains the LisH domain. We further determined that the FOP LisH domain is part of a longer N-terminal segment that is required, albeit not sufficient, for dimerization and centrosomal localization of FOP

Structural basis for potent inhibitory activity of the antibiotic tigecycline during protein synthesis

International audienceHere we present an X-ray crystallography structure of the clinically relevant tigecycline antibiotic bound to the 70S ribosome. Our structural and biochemical analysis indicate that the enhanced potency of tigecycline results from a stacking interaction with nucleobase C1054 within the decoding site of the ribosome. Single-molecule fluorescence resonance energy transfer studies reveal that, during decoding, tigecycline inhibits the initial codon recognition step of tRNA accommodation and prevents rescue by the tetracycline-resistance protein TetM