Control of crosslinking by quaternary structure changes during bacteriophage HK97 maturation.
Radical structural changes drive the maturation of the capsid of HK97, a lambda-like, dsDNA bacteriophage of Escherichia coli. These include expansion from approximately 560 to approximately 660 A in diameter, metamorphosis from a round to an angular shape, and formation of covalent crosslinks between adjacent capsomers. Analogous transformations also occur in unrelated viruses and protein complexes. We find that expansion and crosslinking happen concurrently during maturation at low pH. Expansion causes residues on three different subunits to move up to 35 A to form 420 active sites that each catalyze the formation of a lysine-asparagine crosslink between adjacent subunits, making crosslink formation an indirect reporter of structural change. Intermediate crosslinking patterns support a previously proposed model of expansion, while hydrophobic properties aid in distinguishing discrete intermediates. A structure derived from cryo-EM images reveals the free intermediate conformation of penton arms, supporting our model for coordinated movement of hexons and pentons on the capsid lattice.
Gan
Lu
L
Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
Conway
James F
JF
Firek
Brian A
BA
Cheng
Naiqian
N
Hendrix
Roger W
RW
Steven
Alasdair C
AC
Johnson
John E
JE
Duda
Robert L
RL
D001216:Asparagine / Q000737:chemistry; D017103:Bacillus Phages / Q000737:chemistry* / Q000254:growth & development* / Q000648:ultrastructure; D001665:Binding Sites / Q000502:physiology; D002213:Capsid / Q000737:chemistry* / Q000648:ultrastructure; D036022:Capsid Proteins / Q000737:chemistry* / Q000648:ultrastructure; D020285:Cryoelectron Microscopy; D008239:Lysine / Q000737:chemistry; D011487:Protein Conformation; D020836:Protein Structure, Quaternary / Q000502:physiology; D021122:Protein Subunits / Q000737:chemistry
D036022:Capsid Proteins; D021122:Protein Subunits; D001216:Asparagine; D008239:Lysine