The 12 appendages (blue) are labeled 1 to 12. subtilis infection at or above a specific gp12* concentration ( Villanueva and Salas, 1981).ĭiagram of the Bacteriophage φ29 Tail Showing its Structural Components Purified gp12* from φ29 phage particles is able to saturate host cell surface receptors, preventing B. ![]() subtilis cell wall glucosylated, poly(glycerol phosphate) teichoic acid of strain 168 ( Moreno and Bluzat-Moreno, 1978 Villanueva and Salas, 1981 Young, 1967). Furthermore the sequence of the monomer has some similarity to various polysaccharide binding enzymes ( Xiang et al., 2006 DiMauro et al., 2007). Sequence and structural comparisons suggested that each appendage is a homotrimer of gp12*. In vivo, gp12 is cleaved to produce the ~75KD gp12* assembly attached to the phage particles ( Carrascosa et al., 1974 Tosi et al., 1975). The appendages have a spindle-like shape and are connected to the lower collar through a cylindrical arm. The lower collar is surrounded by 12 appendages (gene product 12, gp12) in up-or-down conformations ( Figure 1) ( Xiang et al., 2006 Tang et al., 2008). The “lower collar” protein assembly at the proximal end of the tail has a bulge and a thin axial tube to which is attached the cylindrical “knob” protein assembly. Folding and assembly of some tailspike proteins are dependent on their C-terminal domains that, in most cases, are proteolytically processed and released ( Gage and Robinson, 2003 Mühlenhoff et al., 2003 Schwarzer et al., 2007).īacteriophage φ29 infects the Gram-positive bacterium, Bacillus subtilis, using a short, 380 Å-long, non-contractile tail ( Anderson and Reilly, 1993). The tail spike triple β-helix often serves as the determinant of bacteriophage host cell specificity. Most phage tailspike proteins are stable, elongated homotrimers and consist of a triple β-helix structure that is able to degrade cell wall glycopolymers ( Weigele et al., 2003). Cell wall glycopolymers are the primary receptors recognized by tailed bacteriophage tailspikes or fiber proteins. Tailed bacteriophages initiate infection of their host cells by reversibly and then irreversibly attaching to cell wall receptors ( Adams, 1959). The cell-wall glycopolymers are highly variable and have been shown to play a role in pathogen infections ( Weidenmaier and Peschel, 2008). The outermost layers of cell walls consist mainly of glycopolymers, such as teichoic acids of Gram-positive bacteria ( Neuhaus and Baddiley, 2003), that are attached either to an inner peptidoglycan layer or to membrane lipids. Structural and sequence comparisons suggest that some eukaryotic and bacterial viruses as well as bacterial adhesins might have similar maturation mechanism as is performed by φ29 gp12 for Bacillus subtilis.īacteria are well protected by complex cell walls. The post-translationally modified N-terminal part has three domains that function to attach the appendages to the phage, digest the cell wall teichoic acids and bind irreversibly to the host, respectively. We also show that auto-cleavage of the C-terminal domain is a post-trimerization event that is followed by a unique ATP-dependent release. We report here crystal structures of the protein before and after catalytic processing and show that the C-terminal domain of gp12 is an “auto-chaperone” that aids trimerization. ![]() In the cell, monomeric gp12 undergoes proteolytic processing that releases the C-terminal domain during assembly into trimers. The tailed bacteriophage φ29 has 12 “appendages” (gene product 12, gp12) attached to its neck region that participate in host cell recognition and entry.
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