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SBNet - Research Reports 1999

Stefan Knight

Position: "Forskare" (SLU)

Project: Structure/function studies of virulence associated adhesion organelles from pathogenic Gram negative bacteria

Name, department, university and co-workers' names

Stefan Knight, Department of Molecular Biology, SLU.

Coworkers: Jenny Berglund, Devapriya Choudhury

Abstract

During 1999 we made a major breakthrough in the field of bacterial pathogenesis: we solved the first three dimensional structure of a virulence-associated bacterial adhesin (FimH) in a complex with its periplasmic chaperone (FimC) (Choudhury et al., Science 1999, 285:1061-1066; Eisenberg, Science 1999, 285:1021-1022; Rebbapragada, Trends in Microbiology 1999, 7: 400). This was the first structure ever of a chaperone with a protein substrate bound to it, and the results, in addition to giving detailed information on the assembly and function of adhesive pili, also have profound implications for how we view protein structure and protein folding. Pilus subunits turned out to be incomplete Ig domains lacking the 7th and final strand of Ig domains. This prevents the subunits from forming a hydrophobic core, and, not surprisingly, pilus subunits cannot fold correctly on their own. The chaperone ameliorates the problem by donating its 7th strand to complete the hydrophobic core of the pilus subunit. Thus, in contrast to conventional wisdom, the FimC-FimH structure reveals an example of a protein where the steric information needed for correct protein folding is not entirely coded by the primary structure of the protein to be folded. Instead, the FimC chaperone appears to function as a template for correct folding by providing an essential component of this information. Based on the structure we were also able to provide the first detailed structural model of a cellular organelle an adhesive pilus. In addition to being of great medical importance, our results thus have far reaching implications for fundamental questions about protein folding and organelle assembly. Work is in progress to express and purify further components of the pilus assembly system as well as components involved in the assembly of type III secretion systems and flagella.

Total budget

100000 SEK + salary for Jenny + salary for Stefan

Sources of funding

SBNet

Publications in refereed scientific journals

1. Choudhury D., Thompson A, Stojanoff V, Langermann S, Pinkner J, Hultgren SJ & Knight SD (1999): X-ray structure of the FimC-FimH Chaperone-Adhesin Complex from Uropathogenic E. coli. Science, 285:1061-1066.

2. Hung DL, Knight SD & Hultgren SJ (1999): Probing conserved surfaces on PapD. Mol. Micro. 31:773-783.

3. Hung DL, Pinkner JS, Knight SD & Hultgren SJ (1999): Structural basis of chaperone self-capping in P pilus biogenesis. Proc. Natl. Acad. Sci. USA 96:8178-8183.

4. Knight SD (2000): RSPS version 4: a semi-interactive vector-search program for solving heavy-atom derivatives. Acta Cryst D56:42-47.

5. Sauer FG, Knight SD, Waksman G & Hultgren SJ (2000): PapD-like chaperones and pilus biogenesis. Sem. Cell. Biol. Rev., in the press.

List of invited lectures

* Uppsala, Sweden (1999). BMC Lecture Series on Molecular and Cellular Biology.

* Newport, Rhode Island, USA (1999), Gordon Research Conference on Molecular Mechanisms of Microbial Adherence

* Glasgow, Scotland (1999), IUCR Congress

* Ventura, CA, USA (2000). Gordon Research Conference on Reversible Associations in Structural and Molecular Biology

List contributions to international conferences

See above

International collaborations (name, affiliation).

Scott Hultgren, Washington University School of Medicine, Department of Molecular Microbiology, St Louis, MO, USA.

Solomon Langermann, MedImmune Inc., Gaithersburg, USA.


SBNet Latest update at 3 April, 2000.