Abstract
The BipA (BPI-inducible protein A) protein is ubiquitously conserved in various bacterial species and belongs to the translational GTPase family. Interestingly, the function of Escherichia coli BipA is not essential for cell growth under normal growth conditions. However, cultivation of bipA-deleted cells at 20°C leads to cold-sensitive growth defect and several phenotypic changes in ribosome assembly, capsule production, and motility, suggesting its global regulatory roles. Previously, our genomic library screening revealed that the overexpressed ribosomal protein (r-protein) L20 partially suppressed cold-sensitive growth defect by resolving the ribosomal abnormality in bipA-deleted cells at low temperature. Here, we explored another genomic library clone containing yebC, which encodes a predicted transcriptional factor that is not directly associated with ribosome biogenesis. Interestingly, overexpression of yebC in bipA-deleted cells diminished capsule synthesis and partially restored lipopolysaccharide (LPS) core maturation at a low temperature without resolving defects in ribosome assembly or motility, indicating that YebC may be specifically involved in the regulation of exopolysaccharide and LPS core synthesis. In this study, we collectively investigated the impacts of bipA-deletion on E. coli capsule, LPS, biofilm formation, and motility and revealed novel roles of YebC in extracellular polysaccharide production and LPS core synthesis at low temperature using this mutant strain. Furthermore, our findings suggest that ribosomal defects as well as increased capsule synthesis, and changes in LPS composition may contribute independently to the cold-sensitivity of bipA-deleted cells, implying multiple regulatory roles of BipA.
Highlights
BipA is a GTPase belonging to translation/elongation factors (TRAFAC) family and shares structural similarity with translational GTPases, such as IF2, EF-Tu, EF-G, EF4, and RF3 (Ero et al, 2016)
We have shown that among them, overexpression of rplT, whose gene product is r-protein L20, partially rescued the ribosomal defects caused by the deletion of bipA at low temperature
The defective biofilm production of pBIS02-2 was not recovered. These findings suggest that biofilm formation was prevented by overproduced capsule in ESC19 cells at 20◦C and that overexpressed YebC resulted in partial restoration of biofilm production by repressing capsule synthesis
Summary
BipA ( known as TypA) is a GTPase belonging to translation/elongation factors (TRAFAC) family and shares structural similarity with translational GTPases (trGTPases), such as IF2, EF-Tu, EF-G, EF4, and RF3 (Ero et al, 2016). It is widely distributed in bacteria and plants (Margus et al, 2007; Wang et al, 2008). Like other ribosome-associated trGTPases, BipA binds to the ribosome only in the GTP-bound form, which in turn stimulates its GTP hydrolysis activity (deLivron and Robinson, 2008; deLivron et al, 2009; Kumar et al, 2015; Choi and Hwang, 2018)
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