The unusual glycine-rich C terminus of the Acinetobacter baumannii RNA chaperone Hfq plays an important role in bacterial physiology

Abstract

is a Gram-negative nosocomial pathogen that causes soft tissue infections in patients who spend a long time in intensive care units. This recalcitrant bacterium is very well known for developing rapid drug resistance, which is a combined outcome of its natural competence and mobile genetic elements. Successful efforts to treat these infections would be aided by additional information on the physiology of Toward that end, we recently reported on a small RNA (sRNA), AbsR25, in this bacterium that regulates the genes of several efflux pumps. Because sRNAs often require the RNA chaperone Hfq for assistance in binding to their cognate mRNA targets, we identified and characterized this protein in The homolog in is a large protein with an extended C terminus unlike Hfqs in other Gram-negative pathogens. The extension has a compositional bias toward glycine and, to a lower extent, phenylalanine and glutamine, suggestive of an intrinsically disordered region. We studied the importance of this glycine-rich tail using truncated versions of Hfq in biophysical assays and complementation of an deletion mutant, finding that the tail was necessary for high-affinity RNA binding. Further tests implicate Hfq in important cellular processes of like metabolism, drug resistance, stress tolerance, and virulence. Our findings underline the importance of the glycine-rich C terminus in RNA binding, ribo-regulation, and auto-regulation of Hfq, demonstrating this hitherto overlooked protein motif to be an indispensable part of the Hfq.

Coping with low water activities and osmotic stress in Acinetobacter baumannii: significance, current status and perspectives

“…One factor known is the RNA chaperone Hfq, which generally acts as mediator of sRNA‐mRNA interactions and thereby has various functions in stress responses of bacteria (Sobrero and Valverde, ). An hfq deletion mutant lost its desiccation resistance to a great extent, and furthermore it was sensitive to a variety of other environmental stresses, such as high and low temperature, low pH and 3% ethanol (Sharma et al ., ). Notably, Hfq of A. baumannii has an extended C‐terminus, which distinguishes the protein from Hfq of other Gram‐negative pathogens.…”

“…Notably, Hfq of A. baumannii has an extended C‐terminus, which distinguishes the protein from Hfq of other Gram‐negative pathogens. This C‐terminus nearly doubles the size of the protein and is important for full function of the RNA chaperone; accordingly, a mutant with a truncated Hfq was more susceptible to desiccation than the wild type (Kuo et al ., ; Sharma et al ., ).…”

Essential Gene Analysis in Acinetobacter baumannii by High-Density Transposon Mutagenesis and CRISPR Interference

“…Transcriptional regulation in A. baumannii shows some unusual features, including a small number of sigma factors (4), a large number of transcriptional regulators that jointly control virulence and antibiotic resistance (22,26,27), and a reliance on the transcriptional regulator Hfq for growth (28,29). Given these features and its divergence from other Gammaproteobacteria, we predicted that the pathogen may encode unidentified essential transcriptional regulators.…”

Identification and Characterization of an RRM-Containing, RNA Binding Protein in Acinetobacter baumannii

“…The relevance of RBPs in A. baumannii is far from being elucidated, but some examples have been reported: the silencing of Csr(A), a global post-transcriptional regulator responsible for metabolisms of glucose, leads to the impairment of the growing abilities of the bacterium [ 8 , 9 ]; the RNA chaperone Hfq, has an important role as a virulence factor, since its knockout leads to reduced growth rate and stress tolerance [ 10 , 11 ]. Several RBP were described to be overexpressed in resistant strains such are enolase, RNAse E and NusA, all involved in mRNA processing and gene expression modulation [ 12 ].…”