| Summary: | 碩士 === 國立陽明大學 === 生命科學系暨基因體科學研究所 === 102 === The PmrA/PmrB two-component system regulates polymyxin-resistance in Gram-negative bacteria. After phosphorylated by the histidine kinase PmrB, the N-terminal receiver domain (RD) of the response regulator PmrA then forms a dimer and the C-terminal DNA-binding domain (DBD) recognizes the tandem repeat sequences of target promoters, initiating transcription of polymyxin-resistant genes.
We solved the 3.2-Å resolution crystal structure of the BeF3−-activated full-length Klebsiella pneumoniae PmrA in complex with a 25-bp DNA. The dimerization of RD and the DBD-DNA interaction is consistent with previous study. However, the intramolecular RD-DBD interface of the two protomers is asymmetric: in one protomer the RD contacts the DBD with a buried surface area of 627.5 Å2, whereas in the other one the two domains are only connected by a linker. This asymmetric interaction may play a role in the PmrA-DNA binding and stabilize the transactivation loop in DBD, which interacts with the σ70 subunit and activates transcription.
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