Title: FimK regulation on the expression of type 1 fimbriae in Klebsiella pneumoniae CG43S3
Authors: Wang, Zhe-Chong
Huang, Ching-Jou
Huang, Ying-Jung
Wu, Chien-Chen
Peng, Hwei-Ling
Department of Biological Science and Technology
Issue Date: 1-Jul-2013
Abstract: Klebsiella pneumoniae CG43, a heavy encapsulated liver abscess isolate, mainly expresses type 3 fimbriae. Type 1 fimbriae expression was only apparent in CG43S3 Delta mrkA (the type 3 fimbriae-deficient strain). The expression of type 1 fimbriae in CG43S3 Delta mrkA was reduced by deleting the fimK gene, but was unaffected by removing the 3' end of fimK encoding the C-terminal EIL domain (EILfimK). Quantitative RT-PCR and promoter activity analysis showed that the putative DNA-binding region at the N terminus, but not the C-terminal EIL domain, of FimK positively affects transcription of the type 1 fimbrial major subunit, fimA. An electrophoretic mobility shift assay demonstrated that the recombinant FimK could specifically bind to fimS, which is located upstream of fimA and contains a vegetative promoter for the fim operon, also reflecting possible transcriptional regulation. EILfimK was shown to encode a functional phosphodiesterase (PDE) via enhancing motility in Escherichia coil JM109 and in vitro using PDE activity assays. Moreover, EILfimK exhibited higher PDE activity than FimK, implying that the N-terminal DNA-binding domain may negatively affect the PDE activity of FimK. FimA expression was detected in CG43S3 expressing EILfimK or AIL(fimK), suggesting that FimA expression is not directly influenced by the c-di-GMP level. In summary, FimK influences type 1 fimbriation by binding to fimS at the N-terminal domain, and thereafter, the altered protein structure may activate C-terminal PDE activity to reduce the intracellular c-di-GMP level.
URI: http://dx.doi.org/10.1099/mic.0.067793-0
ISSN: 1350-0872
DOI: 10.1099/mic.0.067793-0
Volume: 159
Begin Page: 1402
End Page: 1415
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