Dataset Information

Structure of the Capsid Size-Determining Scaffold of "Satellite" Bacteriophage P4.

ABSTRACT: P4 is a mobile genetic element (MGE) that can exist as a plasmid or integrated into its Escherichia coli host genome, but becomes packaged into phage particles by a helper bacteriophage, such as P2. P4 is the original example of what we have termed "molecular piracy", the process by which one MGE usurps the life cycle of another for its own propagation. The P2 helper provides most of the structural gene products for assembly of the P4 virion. However, when P4 is mobilized by P2, the resulting capsids are smaller than those normally formed by P2 alone. The P4-encoded protein responsible for this size change is called Sid, which forms an external scaffolding cage around the P4 procapsids. We have determined the high-resolution structure of P4 procapsids, allowing us to build an atomic model for Sid as well as the gpN capsid protein. Sixty copies of Sid form an intertwined dodecahedral cage around the T = 4 procapsid, making contact with only one out of the four symmetrically non-equivalent copies of gpN. Our structure provides a basis for understanding the sir mutants in gpN that prevent small capsid formation, as well as the nms "super-sid" mutations that counteract the effect of the sir mutations, and suggests a model for capsid size redirection by Sid.

SUBMITTER: Kizziah JL

PROVIDER: S-EPMC7552001 | biostudies-literature | 2020 Aug

REPOSITORIES: biostudies-literature

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Structure of the Capsid Size-Determining Scaffold of "Satellite" Bacteriophage P4.

Kizziah James L JL Rodenburg Cynthia M CM Dokland Terje T

Viruses 20200827 9

P4 is a mobile genetic element (MGE) that can exist as a plasmid or integrated into its <i>Escherichia coli</i> host genome, but becomes packaged into phage particles by a helper bacteriophage, such as P2. P4 is the original example of what we have termed "molecular piracy", the process by which one MGE usurps the life cycle of another for its own propagation. The P2 helper provides most of the structural gene products for assembly of the P4 virion. However, when P4 is mobilized by P2, the resul ...[more]

PMID: 32867300

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Project description:ABSTRACT Analysis of the genetic locus encompassing a cell wall polysaccharide (CWPS) biosynthesis operon of eight strains of Lactococcus lactis, identified as belonging to the same CWPS type C genotype, revealed the presence of a variable region among the strains examined. The results allowed the identification of five subgroups of the C type named subtypes C1 to C5. This variable region contains genes encoding glycosyltransferases that display low or no sequence homology between the subgroups. In this study, we purified an acidic polysaccharide from the cell wall of L. lactis 3107 (subtype C2) and confirmed that it is structurally different from the previously established CWPS of subtype C1 L. lactis MG1363. The CWPS of L. lactis 3107 is composed of pentasaccharide repeating units linked by phosphodiester bonds with the structure 6-?-Glc-3-?-Galf-3-?-GlcNAc-2-?-Galf-6-?-GlcNAc-1-P. Combinations of genes from the variable region of subtype C2 were introduced into a mutant of subtype C1 L. lactis NZ9000 deficient in CWPS biosynthesis. The resulting recombinant mutant synthesized a polysaccharide with a composition characteristic of that of subtype C2 L. lactis 3107 and not wild-type C1 L. lactis NZ9000. By challenging the recombinant mutant with various lactococcal phages, we demonstrated that CWPS is the host cell surface receptor of tested bacteriophages of both the P335 and 936 groups and that differences between the CWPS structures play a crucial role in determining phage host range. IMPORTANCE Despite the efforts of nearly 80 years of lactococcal phage research, the precise nature of the cell surface receptors of the P335 and 936 phage group receptors has remained elusive. This work demonstrates the molecular nature of a P335 group receptor while bolstering the evidence of its role in host recognition by phages of the 936 group and at least partially explains why such phages have a very narrow host range. The information generated will be instrumental in understanding the molecular mechanisms of how phages recognize specific saccharidic receptors located on the surface of their bacterial host.

Dataset Information

Structure of the Capsid Size-Determining Scaffold of "Satellite" Bacteriophage P4.

Publications

Structure of the Capsid Size-Determining Scaffold of "Satellite" Bacteriophage P4.

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