Abstract
HapR is designated as a high cell density quorum sensing master regulatory protein of Vibrio cholerae. It is a member of the TetR family protein and functions both as an activator and a repressor by directly communicating with cognate promoters, thus controlling the expression of a plethora of genes in a density-dependent manner. Molecular insights reveal the domain architecture and further unveil the significance of a cross talk between the DNA binding domain and the dimerization domain for the functionality of the wild-type protein. The DNA binding domain is made up of three α-helices, where a helix-turn-helix motif spans between the helices α2 and α3. The essentiality of the glycine-rich linker linking helices α1 and α2 came into prominence while unraveling the molecular basis of a natural non-functional variant of HapR. Subsequently, the importance of linker length was demonstrated. The present study, involving a series of biochemical analyses coupled with molecular dynamics simulation, has illustrated the indispensability of a critical arginine within the linker at position 37 contributing to HapR–DNA binding activity.
Highlights
Communication is an essential characteristic of life
The alanine variants of the linker region were tested for their capacity to reinstate protease production in V. cholerae strain S7 harboring a non-functional HapR (Supplementary Table 1)
It could be surmised that loss in the protease activity of HapR-R37A could be a result of the instability of the protein under in vivo condition
Summary
Once perceived as organisms that maintain a reclusive lifestyle, participate in intra- and interspecies social networking to shape their behavior in diverse environmental settings. Such communication of the microbial world known as “quorum-sensing” has become a major focus of research. Crystal structure analysis reveals a Linker Mediates Protein DNA Communication two-domain architecture where the N-terminal DNA binding domain comprised three α-helices and the remaining six α-helices are found in the C-terminal-located dimerization domain (De Silva et al, 2007). HapR communicates with cognate promoters by recognizing unique DNA binding motifs (Tsou et al, 2009), thereby fulfilling its commitment as a high cell density master regulator by regulating the constellation of diverse cellular activities. Like HapR, SmcR interacts with many promoters (Kim et al, 2010)
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