Affiliation:
1. Department of Biotechnology St Xavier's College Kolkata India
2. Beamline Development and Application Section Bhabha Atomic Research Centre Mumbai India
Abstract
In Vibrio cholerae, the master regulator FlrA controls transcription of downstream flagellar genes in a σ54‐dependent manner. However, the molecular basis of regulation by VcFlrA, which contains a phosphorylation‐deficient N‐terminal FleQ domain, has remained elusive. Our studies on VcFlrA, four of its constructs, and a mutant showed that the AAA+ domain of VcFlrA, with or without the linker ‘L’, remains in ATPase‐deficient monomeric states. By contrast, the FleQ domain plays a pivotal role in promoting higher‐order functional oligomers, providing the required conformation to ‘L’ for ATP/cyclic di‐GMP (c‐di‐GMP) binding. The crystal structure of VcFlrA‐FleQ at 2.0 Å suggests that distinct structural features of VcFlrA‐FleQ presumably assist in inter‐domain packing. VcFlrA at a high concentration forms ATPase‐efficient oligomers when the intracellular c‐di‐GMP level is low. Conversely, excess c‐di‐GMP locks VcFlrA in a non‐functional lower oligomeric state, causing repression of flagellar biosynthesis.
Funder
Science and Engineering Research Board
Subject
Cell Biology,Genetics,Molecular Biology,Biochemistry,Structural Biology,Biophysics