PMID:22855489

Citation	Quinten, TA and Kuhn, A (2012) Membrane interaction of the portal protein gp20 of bacteriophage T4. J. Virol. 86:11107-14
Abstract	Assembly of the bacteriophage T4 head structure occurs at the cytoplasmic face of the inner membrane of Escherichia coli with the formation of proheads. The proheads contain an internal scaffolding core that determines the size and the structure of the capsid. In a mutant where the major shell protein gp23 was compromised, core structures without a shell had been detected. Such core structures were also found in the mutant T4am20am23. Since the mutation in gene 20 is at the N terminus of gp20, it was assumed that these core structures assemble in the absence of gp20. However, sequencing showed that the mutation introduces a new ribosome binding site that leads to a restart at codon 15. Although the mutant protein gp20s lacks the very N-terminal sequence, we found that it still binds to the membrane of the host cell and can initiate prohead assembly. This explains its activity to allow the assembly of core structures and proheads at the membrane surface. With a cross-linking approach, we show here that gp20 and gp20s are escorted by the chaperones DnaK, trigger factor, and GroEL and dock on the membrane at the membrane protein YidC.
Links	PubMed PMC3457163 Online version:10.1128/JVI.01284-12
Keywords	Amino Acid Sequence; Bacteriophage T4/chemistry; Bacteriophage T4/genetics; Bacteriophage T4/metabolism; Binding Sites; Capsid/metabolism; Capsid/ultrastructure; Capsid Proteins/chemistry; Capsid Proteins/genetics; Capsid Proteins/metabolism; Cell Membrane/metabolism; Cell Membrane/virology; Chaperonin 60/metabolism; Escherichia coli/genetics; Escherichia coli/metabolism; Escherichia coli/virology; Escherichia coli Proteins/metabolism; HSP70 Heat-Shock Proteins/metabolism; Membrane Transport Proteins/metabolism; Mutant Proteins/chemistry; Mutant Proteins/metabolism; Peptidylprolyl Isomerase/metabolism; Sequence Analysis, DNA; Viral Proteins/genetics; Viral Proteins/metabolism; Virus Assembly
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
BPT4:PORTL		GO:0020002: host cell plasma membrane	ECO:0000314:		C		Fig 7,Protease mapping of His-gp20 and His-gp20s, shows Both His-gp20 and His-gp20s were not digested by the protease mapping, compared with OmpA. So both proteins are most likely peripherally bound to the cytoplasmic surface of the inner membrane.	complete CACAO 12593

References

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