title: Identification of protein domains on major pilin MrkA that affects the mechanical properties of Klebsiella pneumoniae type 3 fimbriae.
abstract: The Klebsiella pneumoniae type 3 fimbriae are mainly composed of MrkA pilins that assemble into a helixlike filament. This study determined the biomechanical properties of the fimbriae and analyzed 11 site-directed MrkA mutants to identify domains that are critical for the properties. Escherichia coli strains expressing type 3 fimbriae with an Ala substitution at either F34, V45, C87, G189, T196, or Y197 resulted in a significant reduction in biofilm formation. The E. coli strain expressing MrkAG189A remained capable of producing a normal number of fimbriae. Although F34A, V45A, T196A, and Y197A substitutions expressed on E. coli strains produced sparse quantities of fimbriae, no fimbriae were observed on the cells expressing MrkAC87A. Further investigations of the mechanical properties of the MrkAG189A fimbriae with optical tweezers revealed that, unlike the wild-type fimbriae, the uncoiling force for MrkAG189A fimbriae was not constant. The MrkAG189A fimbriae also exhibited a lower enthalpy in the differential scanning calorimetry analysis. Together, these findings indicate that the mutant fimbriae are less stable than the wild-type. This study has demonstrated that the C-terminal β strands of MrkA are required for the assembly and structural stability of fimbriae.
authors.affiliation: Institute and Department of Electrophysics, National Chiao Tung University, 1001 University Road, Hsinchu 300, Taiwan, Republic of China.
authors.forename: Chia-Han
authors.initials: CH
authors.lastname: Chan
authors.forename: Feng-Jung
authors.initials: FJ
authors.lastname: Chen
authors.forename: Ying-Jung
authors.initials: YJ
authors.lastname: Huang
authors.forename: Shin-Yu
authors.initials: SY
authors.lastname: Chen
authors.forename: Kuo-Liang
authors.initials: KL
authors.lastname: Liu
authors.forename: Zhe-Chong
authors.initials: ZC
authors.lastname: Wang
authors.forename: Hwei-Ling
authors.initials: HL
authors.lastname: Peng
authors.forename: Tri-Rung
authors.initials: TR
authors.lastname: Yew
authors.forename: Cheng-Hsien
authors.initials: CH
authors.lastname: Liu
authors.forename: Gunn-Guang
authors.initials: GG
authors.lastname: Liou
authors.forename: Ken Y
authors.initials: KY
authors.lastname: Hsu
authors.forename: Hwan-You
authors.initials: HY
authors.lastname: Chang
authors.forename: Long
authors.initials: L
authors.lastname: Hsu
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D018441:Biofilms; D036781:Fimbriae Proteins / Q000737:chemistry / Q000378:metabolism*; D007711:Klebsiella pneumoniae / Q000378:metabolism*; D017434:Protein Structure, Tertiary
chemical_list: D001426:Bacterial Proteins; D036781:Fimbriae Proteins