Capsid localization of the bacteriophage P4 Psu protein.
In addition to its polarity-suppressing activity, the Psu protein of bacteriophage P4 also serves to stabilize the capsid against heat treatment and binds externally to the phage capsid. However, the heat stability is lost upon purification of the virus, indicating a loss of Psu protein from the capsid. By using three-dimensional reconstruction from cryo-electron micrographs of P4 psu1 amber mutants lacking Psu, and of P4 virions, which have been saturated with Psu protein to regain heat stability, we have determined the position of this protein on the virus surface. Our results are consistent with the hypothesis that the function of Psu is to stabilize the hexameric capsomer assembly.
European Molecular Biology Laboratory, Heidelberg, Germany.
T
T
Dokland
M L
ML
Isaksen
S D
SD
Fuller
B H
BH
Lindqvist
D002213:Capsid / Q000302:isolation & purification* / Q000648:ultrastructure*; D036022:Capsid Proteins; D003090:Coliphages / Q000648:ultrastructure*; D015925:Cryopreservation; D003673:Defective Viruses / Q000648:ultrastructure*; D007091:Image Processing, Computer-Assisted; D008854:Microscopy, Electron; D008961:Models, Structural; D009154:Mutation; D014771:Virion / Q000648:ultrastructure
D036022:Capsid Proteins; C074513:polarity suppression factor, bacteriophage P4