RESUMO
Incorporation of the amino acid selenocysteine into a growing protein chain involves the interaction between a hairpin in the mRNA termed the selenocysteine insertion sequence (SECIS) and the special elongation factor SelB. Here we present the structure of the SECIS from the thermophilic organism Moorella thermoacetica (SECIS-MT) determined using nuclear magnetic resonance (NMR) spectroscopy. The SECIS-MT hairpin structure contains a pentaloop with the first and fourth nucleotides of the loop forming a noncanonical GC base pair; the fifth loop nucleotide is bulged out and unstructured. The G and U in positions two and three are on opposite sides of the loop and solvent exposed. The backbone resonances of the SECIS-binding domain from the M. thermoacetica SelB protein were assigned, and the degree of chemical shift perturbations that occur upon SECIS binding were mapped onto the structure of the complex. We demonstrate that a region in the third winged-helix domain of SelB, not previously implicated in binding, is affected by SECIS binding.
Assuntos
Proteínas de Bactérias/química , Fatores de Alongamento de Peptídeos/química , RNA Bacteriano/química , Selenocisteína/metabolismo , Proteínas de Bactérias/metabolismo , Sequência de Bases , Sítios de Ligação , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Dados de Sequência Molecular , Conformação de Ácido Nucleico , Fatores de Alongamento de Peptídeos/metabolismoRESUMO
We report the identification of a novel compound that binds to the Escherichia coli 16S ribosomal A-site. Binding by the compound was observed using nuclear magnetic resonance and mass spectrometry techniques. We show that the compound binds in the same position in the A-site RNA as occupied by the aminoglycoside class of antibiotics.
