Characterization of three small proteins in Brucella abortus linked to fucose utilization

Abstract

Elucidating the function of proteins < 50 amino acids in length is no small task. Nevertheless, small proteins can play vital roles in the lifestyle of bacteria and influence the virulence of pathogens; thus, the investigation of the small proteome is warranted. Recently, our group identified the Brucella abortus protein VtlR as a transcriptional activator of four genes, one of which is the well-studied small regulatory RNA AbcR2, while the other three genes encode hypothetical small proteins, two of which are highly conserved among the order Rhizobiales. This study provides evidence that all three genes encode authentic small proteins and that all three are highly expressed under oxidative stress, low-pH, and stationary-phase growth conditions. Fractionation of the cells revealed that the proteins are localized to the membranes of B. abortus. We demonstrate that the small proteins under the transcriptional control of VtlR are not accountable for attenuation observed with the B. abortus vtlR deletion strain. However, there is an association between VtlR-regulated genes and growth inhibition in the presence of the sugar L-fucose. Subsequent transcriptomic analyses revealed that B. abortus initiates the transcription of a locus encoding a putative sugar transport and utilization system when the bacteria are cultured in the presence of L-fucose. Altogether, our observations characterize the role of the VtlR-controlled small proteins BAB1_0914, BAB2_0512, and BAB2_0574 in the biology of B. abortus, particularly in the capacity of the bacteria to utilize L-fucose.