PSI Structural Biology Knowledgebase

PSI | Structural Biology Knowledgebase
Header Icons

Related Articles
Community-Nominated Targets
July 2015
Drug Discovery: Solving the Structure of an Anti-hypertension Drug Target
July 2015
Retrospective: 7,000 Structures Closer to Understanding Biology
July 2015
Design and Evolution: Unveiling Translocator Proteins
June 2015
Signaling with DivL
May 2015
Signaling: A Platform for Opposing Functions
May 2015
Signaling: Securing Lipid-Protein Partnership
May 2015
Dynamic DnaK
March 2015
Iron-Sulfur Cluster Biosynthesis
December 2014
Mitochondrion: Flipping for UCP2
December 2014
Mitochondrion: Setting a New TRAP1
December 2014
Power in Numbers
August 2014
Quorum Sensing: A Groovy New Component
August 2014
Quorum Sensing: E. coli Gets Involved
August 2014
iTRAQing the Ubiquitinome
July 2014
Microbiome: The Dynamics of Infection
September 2013
Protein-Nucleic Acid Interaction: A Modified SAM to Modify tRNA
July 2013
Protein-Nucleic Acid Interaction: Versatile Glutamate
July 2013
PDZ Domains
April 2013
Alpha-Catenin Connections
March 2013
Cell-Cell Interaction: A FERM Connection
March 2013
Cell-Cell Interaction: Magic Structure from Microcrystals
March 2013
Cell-Cell Interaction: Modulating Self Recognition Affinity
March 2013
Bacterial Hemophores
January 2013
Archaeal Lipids
December 2012
Membrane Proteome: Capturing Multiple Conformations
December 2012
Lethal Tendencies
October 2012
Symmetry from Asymmetry
October 2012
A signal sensing switch
September 2012
Regulatory insights
September 2012
AlkB Homologs
August 2012
Budding ensemble
August 2012
Targeting Enzyme Function with Structural Genomics
July 2012
The machines behind the spindle assembly checkpoint
June 2012
Chaperone interactions
April 2012
Pilus Assembly Protein TadZ
April 2012
Revealing the Nuclear Pore Complex
March 2012
Topping off the proteasome
March 2012
Twist to open
March 2012
Disordered Proteins
February 2012
Analyzing an allergen
January 2012
Making Lipopolysaccharide
January 2012
Pulling on loose ends
January 2012
Terminal activation
December 2011
The Perils of Protein Secretion
November 2011
Bacterial Armor
October 2011
TLR4 regulation: heads or tails?
October 2011
Ribose production on demand
September 2011
Moving some metal
August 2011
Looking for lipids
July 2011
Ribofuranosyl Binding Protein
June 2011
A molecular switch for neuronal growth
May 2011
Cell wall recycler
May 2011
Added benefits
April 2011
NMR challenges current protein hydration dogma
March 2011
Nitrile Reductase QueF
March 2011
Tip formin
March 2011
Inhibiting factor
February 2011
PASK staying active
February 2011
Tryptophanyl-tRNA Synthetase
February 2011
Regulating nitrogen assimilation
January 2011
Subtle shifts
January 2011
December 2010
Function following form
October 2010
tRNA Isopentenyltransferase MiaA
August 2010
Importance of extension for integrin
June 2010
April 2010
Alg13 Subunit of N-Acetylglucosamine Transferase
February 2010
Hemolysin BL
January 2010
December 2009
Two-component signaling
December 2009
Network coverage
November 2009
Pseudouridine Synthase TruA
November 2009
Unusual cell division
October 2009
Toxin-antitoxin VapBC-5
September 2009
Salicylic Acid Binding Protein 2
August 2009
Proofreading RNA
July 2009
Ykul structure solves bacterial signaling puzzle
July 2009
Hda and DNA Replication
June 2009
Controlling p53
May 2009
Mitotic checkpoint control
May 2009
Ribonuclease and Ribonuclease Inhibitor
April 2009
The elusive helicase
April 2009
March 2009
High-energy storage system
February 2009
A new class of bacterial E3 ubiquitination enzymes
January 2009
Poly(A) RNA recognition
January 2009
Activating BAX
December 2008
Scavenger Decapping Enzyme DcpS
November 2008
Bacteriophage Lambda cII Protein
October 2008
New metal-binding domain
October 2008
Blocking AmtB
September 2008
September 2008
Aspartate Dehydrogenase
August 2008
RNase T
July 2008
May 2008

Research Themes Cell biology

Pilus Assembly Protein TadZ

SBKB [doi:10.3942/psi_sgkb/fm_2012_4]
Featured System - April 2012
Short description: Many bacteria are covered with long filaments, called pili or fimbriae, that help them interact and attach to their environment.

Many bacteria are covered with long filaments, called pili or fimbriae, that help them interact and attach to their environment. Typically the genomes of these bacteria have a large locus of genes that encode proteins for the synthesis, localization and assembly of these filaments. As part of a community-nominated project, JCSG researchers have solved the structure of one of these proteins, TadZ (PDB entry 3fkq), and from it, discovered its function.

Pili and Pilin

Pili come in several shapes and sizes. The ones shown here on the left, extending from the surface of an Escherichia coli cell, are termed "type I" pili. They are built using a complex usher system that guides subunits to the surface, assembles them, and pushes them out through a narrow pore in the cell surface. The pilin subunit on the right (PDB entry 1ay2) is different, termed "type IV" pilin, which is built using an ATP-driven motor and a large circular pore. Pilin proteins have a characteristic shape, with a globular domain that forms the outer surface of the fiber, and a long hydrophic tail that packs into the middle of the fiber. This unique structure forms a filament that is very narrow, but also extremely strong.

Sticky Business

Understanding of pilus form and function is important, since pili play central roles in many pathogenic bacteria. For instance, the pili of the bacterium Aggregatibacter actinomycetemcomitans are essential for their adhesion to teeth. They form tenacious biofilms on the surface of teeth, which can lead to periodontal disease. Hopefully, greater understanding of the mechanisms of this adhesion will allow us to develop effective treatments to remove the bacteria.

Structure and Function of TadZ

Biochemical studies have shown that TadZ is important for the localization of pili to the poles of these bacteria, which is required for biofilm formation. Comparison of TadZ with similar proteins provides clues for how this might happen. The protein is composed of two domains. The smaller domain is very similar to signaling proteins like CheY, which use protein-protein interactions to transmit cellular information. TadZ, however, is missing some of the key elements used in this signaling, such as the ability to bind to magnesium and a key aspartate amino acid that is phosphorylated. The large domain is similar to several proteins that cleave ATP in their function. TadZ has a similar ATP binding site--in fact, ATP was serendipitously found in the crystal structure, presumably carried along during the entire process of purification of the protein. However, TadZ cleaves ATP more slowly, so JCSG researchers now see TadZ as a molecular hub, using its protein-binding domain to recruit other pilus-constructing proteins, and using ATP to strengthen the connection between its two subunits. To explore these structures in more detail, the JSmol tab below displays an interactive JSmol.


TadZ Domain Comparisons(PDB entries 3fkq, 2che, and 2bek)

The two TadZ domains are compared to two proteins with similar folds (use the buttons to display them). The smaller domain is similar to other protein-protein signaling proteins like CheY. However, CheY has a special aspartate that gets phosphorylated (shown in green) and it binds to a magnesium ion (in yellow), both of which are important in its function and are not present in TadZ. The larger domain is similar to ATPases like Soj. However, the ATP-binding site of TadZ has lost some important m


  1. Xu, Q. et al. Structure of the pilus assembly protein TadZ from Eubacterium rectale: implications for polar localization. Mol. Microbiol. 83, 712-727 (2012).

  2. Perez-Cheeks, B. A. et al. The product of TadZ, a new member of the parA/minD superfamily, localizes to a pole in Aggregatibacter actinomycetemcomitans. Mol. Microbiol. 83, 694-711 (2012).

  3. Proft, T. & Baker, E. N. Pili in gram-negative and gram-positive bacteria -- structure, assembly and their role in disease. Cell. Mol. Life Sci. 66, 613-635 (2009).

  4. Craig, L., Pique, M. E. & Tainer, J. A. Type IV pilus structure and bacterial pathogenicity. Nat. Rev. Microbio. 2, 363-378 (2004).

References to Structures

  1. 3fkq - Xu, Q. et al. Structure of the pilus assembly protein TadZ from Eubacterium rectale: implications for polar localization. Mol. Microbiol. 83, 712-727 (2012).

  2. 2bek - Leonard, T. A., Butler, P. J. & Lowe, J. Bacterial chromosome segregation: structure and DNA binding of Soj dimer--a conserved biological switch. EMBO J. 24, 270-282 (2005).

  3. 1ay2 - Parge, H. E., Forest, K. T., Hickey, M. J., Christensen, D. A., Getzoff, E. D. & Tainer, J. A. Structure of the fibre-forming protein pilin at 2.6 A resolution. Nature 378, 32-38 (1995).

  4. 2che - Stock, A. M. et al. Structure of the Mg(2+)-bound form of CheY and mechanism of phosphoryl transfer in bacterial chemotaxis. Biochemistry 32, 13375-13380 (1993).

Structural Biology Knowledgebase ISSN: 1758-1338
Funded by a grant from the National Institute of General Medical Sciences of the National Institutes of Health