Determinants of bacteriophage phi29 head morphology.
Bacteriophage phi29 requires scaffolding protein to assemble the 450 x 540 A prolate prohead with T = 3 symmetry end caps. In infections with a temperature-sensitive mutant scaffolding protein, capsids assemble predominantly into 370 A diameter isometric particles with T = 3 symmetry that lack a head-tail connector. However, a few larger, 430 A diameter, particles are also assembled. Cryo-electron microscopy shows that these larger particles are icosahedral with T = 4 symmetry. The prolate prohead, as well as the two isometric capsids with T = 3 and T = 4 symmetry, are composed of similar pentamers and differently skewed hexamers. The skewing of the hexamers in the equatorial region of proheads and in the T = 4 isometric particles reflects their different environments. One of the functions of the scaffolding protein, present in the prohead, may be to stabilize skewed hexamers during assembly.
Choi
Kyung H
KH
Department of Biological Sciences, Purdue University, 915 West State Street, West Lafayette, Indiana 47907.
Morais
Marc C
MC
Anderson
Dwight L
DL
Rossmann
Michael G
MG
D001412:Bacillus subtilis / Q000378:metabolism; D001671:Biochemistry / Q000379:methods; D036022:Capsid Proteins / Q000737:chemistry*; D020285:Cryoelectron Microscopy / Q000379:methods*; D007658:Ketone Oxidoreductases / Q000378:metabolism*; D008958:Models, Molecular; D008968:Molecular Conformation; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D014764:Viral Proteins / Q000737:chemistry
D036022:Capsid Proteins; D014764:Viral Proteins; C097975:portal protein, bacteriophage phi29; D007658:Ketone Oxidoreductases