Dataset Information

Crystal and cryoEM structural studies of a cell wall degrading enzyme in the bacteriophage phi29 tail.

ABSTRACT: The small bacteriophage phi29 must penetrate the approximately 250-A thick external peptidoglycan cell wall and cell membrane of the Gram-positive Bacillus subtilis, before ejecting its dsDNA genome through its tail into the bacterial cytoplasm. The tail of bacteriophage phi29 is noncontractile and approximately 380 A long. A 1.8-A resolution crystal structure of gene product 13 (gp13) shows that this tail protein has spatially well separated N- and C-terminal domains, whose structures resemble lysozyme-like enzymes and metallo-endopeptidases, respectively. CryoEM reconstructions of the WT bacteriophage and mutant bacteriophages missing some or most of gp13 shows that this enzyme is located at the distal end of the phi29 tail knob. This finding suggests that gp13 functions as a tail-associated, peptidoglycan-degrading enzyme able to cleave both the polysaccharide backbone and peptide cross-links of the peptidoglycan cell wall. Comparisons of the gp13(-) mutants with the phi29 mature and emptied phage structures suggest the sequence of events that occur during the penetration of the tail through the peptidoglycan layer.

SUBMITTER: Xiang Y

PROVIDER: S-EPMC2474476 | biostudies-literature | 2008 Jul

REPOSITORIES: biostudies-literature

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Crystal and cryoEM structural studies of a cell wall degrading enzyme in the bacteriophage phi29 tail.

Xiang Ye Y Morais Marc C MC Cohen Daniel N DN Bowman Valorie D VD Anderson Dwight L DL Rossmann Michael G MG

Proceedings of the National Academy of Sciences of the United States of America 20080707 28

The small bacteriophage phi29 must penetrate the approximately 250-A thick external peptidoglycan cell wall and cell membrane of the Gram-positive Bacillus subtilis, before ejecting its dsDNA genome through its tail into the bacterial cytoplasm. The tail of bacteriophage phi29 is noncontractile and approximately 380 A long. A 1.8-A resolution crystal structure of gene product 13 (gp13) shows that this tail protein has spatially well separated N- and C-terminal domains, whose structures resemble ...[more]

PMID: 18606992

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Project description:Bacteriophage alpha3 is a member of the Microviridae, a family of small, single-stranded, icosahedral phages that include phiX174. These viruses have an ssDNA genome associated with approximately 12 copies of an H pilot protein and 60 copies of a small J DNA-binding protein. The surrounding capsid consists of 60 F coat proteins decorated with 12 pentameric spikes of G protein. Assembly proceeds via a 108S empty procapsid that requires the external D and internal B scaffolding proteins for its formation. The alpha3 "open" procapsid structural intermediate was determined to 15A resolution by cryo-electron microscopy (cryo-EM). Unlike the phiX174 "closed" procapsid and the infectious virion, the alpha3 open procapsid has 30A wide pores at the 3-fold vertices and 20A wide gaps between F pentamers as a result of the disordering of two helices in the F capsid protein. The large pores are probably used for DNA entry and internal scaffolding protein exit during DNA packaging. Portions of the B scaffolding protein are located at the 5-fold axes under the spike and in the hydrophobic pocket on the inner surface of the capsid. Protein B appears to have autoproteolytic activity that cleaves at an Arg-Phe motif and probably facilitates the removal of the protein through the 30A wide pores. The structure of the alpha3 mature virion was solved to 3.5A resolution by X-ray crystallography and was used to interpret the open procapsid cryo-EM structure. The main differences between the alpha3 and phiX174 virion structures are in the spike and the DNA-binding proteins. The alpha3 pentameric spikes have a rotation of 3.5 degrees compared to those of phiX174. The alpha3 DNA-binding protein, which is shorter by 13 amino acid residues at its amino end when compared to the phiX174 J protein, retains its carboxy-terminal-binding site on the internal surface of the capsid protein. The icosahedrally ordered structural component of the ssDNA appears to be substantially increased in alpha3 compared to phiX174, allowing the building of about 10% of the ribose-phosphate backbone.

Dataset Information

Crystal and cryoEM structural studies of a cell wall degrading enzyme in the bacteriophage phi29 tail.

Publications

Crystal and cryoEM structural studies of a cell wall degrading enzyme in the bacteriophage phi29 tail.

Similar Datasets

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