%0 Journal Article %A Wang, Zhe-Chong %A Huang, Ching-Jou %A Huang, Ying-Jung %A Wu, Chien-Chen %A Peng, Hwei-Ling %T FimK regulation on the expression of type 1 fimbriae in Klebsiella pneumoniae CG43S3 %D 2013 %J Microbiology, %V 159 %N Pt_7 %P 1402-1415 %@ 1465-2080 %R https://doi.org/10.1099/mic.0.067793-0 %I Microbiology Society, %X Klebsiella pneumoniae CG43, a heavy encapsulated liver abscess isolate, mainly expresses type 3 fimbriae. Type 1 fimbriae expression was only apparent in CG43S3ΔmrkA (the type 3 fimbriae-deficient strain). The expression of type 1 fimbriae in CG43S3ΔmrkA was reduced by deleting the fimK gene, but was unaffected by removing the 3′ end of fimK encoding the C-terminal EIL domain (EIL fimK ). 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. EIL fimK was shown to encode a functional phosphodiesterase (PDE) via enhancing motility in Escherichia coli JM109 and in vitro using PDE activity assays. Moreover, EIL fimK 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 EIL fimK 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. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.067793-0