Fimk regulation on the expression of type 1 fimbriae in Klebsiella pneumoniae CG43S3

Zhe Chong Wang, Ching Jou Huang, Ying Jung Huang, Chien Chen Wu, Hwei-Ling Peng*

*Corresponding author for this work

Research output: Contribution to journalArticle

9 Scopus citations

Abstract

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 fimbriaedeficient strain). The expression of type 1 fimbriae in CG43S3DmrkA was reduced by deleting the fimK gene, but was unaffected by removing the 39 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 coli 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 AILfimK, 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.

Original languageEnglish
Pages (from-to)1402-1415
Number of pages14
JournalMicrobiology (United Kingdom)
Volume159
Issue numberPART7
DOIs
StatePublished - 1 Jul 2013

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