Abstract
The bacterial type IV pilus (T4P) is the strongest biological motor known to date as its retraction can generate forces well over 100 pN. Myxococcus xanthus, a δ-proteobacterium, provides a good model for T4P investigations because its social (S) gliding motility is powered by T4P. In this study, the interactions among M. xanthus T4P proteins were investigated using genetics and the yeast two-hybrid (Y2H) system. Our genetic analysis suggests that there is an integrated T4P structure that crosses the inner membrane (IM), periplasm and the outer membrane (OM). Moreover, this structure exists in the absence of the pilus filament. A systematic Y2H survey provided evidence for direct interactions among IM and OM proteins exposed to the periplasm. For example, the IM lipoprotein PilP interacted with its cognate OM protein PilQ. In addition, interactions among T4P proteins from the thermophile Thermus thermophilus were investigated by Y2H. The results indicated similar protein-protein interactions in the T4P system of this non-proteobacterium despite significant sequence divergence between T4P proteins in T. thermophilus and M. xanthus. The observations here support the model of an integrated T4P structure in the absence of a pilus in diverse bacterial species.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Amino Acid Sequence
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Bacterial Proteins / chemistry
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Bacterial Proteins / genetics
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Bacterial Proteins / metabolism*
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Cytoplasm
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Fimbriae, Bacterial / chemistry
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Fimbriae, Bacterial / genetics
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Fimbriae, Bacterial / metabolism*
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Gene Deletion
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Molecular Sequence Data
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Myxococcus xanthus / chemistry
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Myxococcus xanthus / cytology
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Myxococcus xanthus / genetics
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Myxococcus xanthus / metabolism*
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Protein Interaction Maps
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Thermus thermophilus / chemistry
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Thermus thermophilus / cytology
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Thermus thermophilus / genetics
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Thermus thermophilus / metabolism*
Grants and funding
This work was partially supported by the National Institutes of Health, the National Science Foundation and Fralin Life Science Institute. CL was partially supported by the China Scholarship Council. RAW was partially supported by the Post Baccalaureate Research and Education Program (PREP) and the Multicultural Academic Opportunities Program (MAOP) at Virginia Tech. The publication of this article is supported by Virginia Tech's Open Access Subvention Fund. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.