PMID: 23954502

Authors:

Morris ER, Hall G, Li C, Heeb S, Kulkarni RV, Lovelock L, Silistre H, Messina M, Camara M, Emsley J, Williams P, Searle MS

Title:

Structural Rearrangement in an RsmA/CsrA Ortholog of Pseudomonas aeruginosa Creates a Dimeric RNA-Binding Protein, RsmN.

Journal:

Structure. 2013 Aug 13. pii: S0969-2126(13)00257-8. doi:, 10.1016/j.str.2013.07.007.

Abstract:

In bacteria, the highly conserved RsmA/CsrA family of RNA-binding proteins functions as global posttranscriptional regulators acting on mRNA translation and stability. Through phenotypic complementation of an rsmA mutant in Pseudomonas aeruginosa, we discovered a family member, termed RsmN. Elucidation of the RsmN crystal structure and that of the complex with a hairpin from the sRNA, RsmZ, reveals a uniquely inserted alpha helix, which redirects the polypeptide chain to form a distinctly different protein fold to the domain-swapped dimeric structure of RsmA homologs. The overall beta sheet structure required for RNA recognition is, however, preserved with compensatory sequence and structure differences, allowing the RsmN dimer to target binding motifs in both structured hairpin loops and flexible disordered RNAs. Phylogenetic analysis indicates that, although RsmN appears unique to P. aeruginosa, homologous proteins with the inserted alpha helix are more widespread and arose as a consequence of a gene duplication event.