3qsu

Publication Abstract from PubMed

Hfq is a post-transcriptional regulator that plays a key role in bacterial gene expression by binding AU-rich sequences and A-tracts to facilitate the annealing of sRNAs to target mRNAs and to affect RNA stability. To understand how Hfq from the Gram-positive bacterium Staphylococcus aureus (Sa) binds A-tract RNA, we determined the crystal structure of an Sa Hfq-adenine oligoribonucleotide complex. The structure reveals a bipartite RNA-binding motif on the distal face that is composed of a purine nucleotide-specificity site (R-site) and a non-discriminating linker site (L-site). The (R-L)-binding motif, which is also utilized by Bacillus subtilis Hfq to bind (AG)(3)A, differs from the (A-R-N) tripartite poly(A) RNA-binding motif of Escherichia coli Hfq whereby the Sa Hfq R-site strongly prefers adenosine, is more aromatic and permits deeper insertion of the adenine ring. R-site adenine-stacking residue Phe30, which is conserved among Gram-positive bacterial Hfqs, and an altered conformation about beta3 and beta4 eliminate the adenosine-specificity site (A-site) and create the L-site. Binding studies show that Sa Hfq binds (AU)(3)A approximately (AG)(3)A >/= (AC)(3)A > (AA)(3)A and L-site residue Lys33 plays a significant role. The (R-L) motif is likely utilized by Hfqs from most Gram-positive bacteria to bind alternating (A-N)(n) RNA.

Structural mechanism of Staphylococcus aureus Hfq binding to an RNA A-tract.,Horstmann N, Orans J, Valentin-Hansen P, Shelburne SA 3rd, Brennan RG Nucleic Acids Res. 2012 Sep 10. PMID:22965117^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.