TABLE V.

P22 intraphage protein interactions

P22 1	P22 2	Description	References
gp3	gp3	Small terminase subunit; homononomer in solution	Nemecek et al., 2007, 2008
gp3	gp2	Purify as complex; bind each other in vitro	Nemecek et al., 2007; Poteete and Botstein, 1979
gp2	gp1	gp2 is large terminase subunit; assembles in packaging motor to gp1 by analogy with other phages (gp2 by itself is monomer in solution); evolutionary argument for P22 gp2–gp1 interaction	Casjens, 2011
gp1	gp1	Portal protein; homododecamer; EM of 12-mer; EM of virion; X-ray structure	Bazinet et al., 1988; Lander et al., 2006; Olia et al., 2011
gp1	gp5	Purify as complex (procapsids); three-dimensional (3D) reconstructions of virion and procapsid	Botstein et al., 1973; Chen et al., 2011; Lander et al., 2006
gp1	gp8	gp8 required for assembly of gp1 into procapsid; interaction seen in procapsid 3D reconstruction	Chen et al., 1989; Greene and King, 1996; Weigele et al., 2005
gp8	gp8	Scaffolding protein; forms homodimers and tetramers in solution	Parker et al., 1997
gp8	gp5	Purify as complex (procapsid); bind in vitro	Fuller and King, 1982; Greene and King, 1994; Parker et al., 1998
gp5	gp5	Coat (major capsid) protein; forms T=7 l icosahedral shell of virion	Botstein et al., 1973; Casjens, 1979; Lander et al., 2006
gp5	gp1	Purify as complex (procapsids); interaction seen in 3D reconstruction	Chen et al., 2011; Lander et al., 2006
gp4	gp4	Tail protein; monomer in solution (naturally unfolded?); gp4s barely touching each other in dodecamer ring in virion (i.e., contacts not large); EM, X-ray structure	Olia et al., 2011; Tang et al., 2011
gp4	gp5	Contact in high-resolution 3D reconstruction of virion	Olia et al., 2006, 2011; Tang et al., 2011
gp4	gp1	Order of assembly, EM, 3D reconstruction; X-ray cocrystal structure	Olia et al., 2006, 2011; Tang et al., 2011
gp4	gp10	12 gp4s contact 6 gp10s; order of assembly, EM, 3D reconstruction	Lander et al., 2006; Olia et al., 2007
gp4	gp9	gp4 ring contacts 6 gp9 trimers; 3D reconstruction	Lander et al., 2006
gp10	gp10	Tail protein; probably hexamer in solution; 3D reconstruction	Lander et al., 2006; Olia et al., 2007
gp10	gp9	6 gp4s contact 6 gp9 trimers; 3D reconstruction	Lander et al., 2006
gp10	gp26	6 gp10s contact one gp26 trimer	Landeret al., 2006
gp26	gp26	Tail needle protein; trimer in solution - crystal structure; one trimer in virion	Olia et al., 2007
gp16	gp8	Mutants of gp8 do not incorporate gp16 into virion	Chen et al., 1989; Greene and King, 1996; Weigele et al., 2005
C1	C1	C1 is homologue of λ CII; homotetramer	Ho et al., 1992
Mnt	Mnt	Repressor of antirepressor gene; tetramer	Nooren et al., 1999
Arc	Arc	Repressor of antirepressor gene; dimer in solution, tetramer on DNA	Bowie and Sauer, 1989; Breg et al., 1990; Brown, Bowie and Sauer, 1990
Ant	C2	Antirepressor; binds to and inhibits C2 repressor	Susskind and Botstein, 1975
gp9	gp9	Tailspike protein; trimer in solution, 6 trimers in virion; crystal structure; binds to polysaccharide on cell surface	Lander et al., 2006; Steinbacher et al., 1994, 1997
Int	Xis	Form heteromultimer	Cho et al., 2002
Xis	Xis	Excisionase; homomultimers	Mattis et al., 2008
Erf	Erf	Recombination protein; homomultimeric ring of 10–14 subunits	Poteete et al., 1983
C3	C3	C3 is homologue of λ CIII; λ CIII is dimer by disulfide bond; P22 interaction by homology with λ CIII	Halder et al., 2007
SieB	Esc	Similar to λ but not studied in detail	Ranade and Poteete, 1993a
C2	C2	Prophage repressor homologue of λ CI; homodimer	De Anda et al., 1983
Cro	Cro	Dimer; solution studies and crystal structure	Darling et al., 2000; Newlove et al., 2004
gp18	gp12	Origin binding protein gp18 recruits DnaB-like gp12 to replication origin by analogy with λ (note that gp12 is not a homologue of λ P protein; gp18 is homologous to λ O protein only in N-terminal domain)	Backhaus and Petri, 1984
Rz	Rz1	Rz and Rz1 are supposed to bind to one another and form a bridge that spans the periplasm in phage λ; P22 gp15 and Rz1 should do the same by homology.	Summer et al., 2007
gp13	gp13	Holin forms rings of large diameter in λ; by homology same should be true of P22 holin	Savva et al., 2008
gp13	gp13′	Antiholin–holin interactions delay the formation of holin rings in λ; by homology same should be true in P22	Rennell and Poteete, 1985
Dec	Dec	Trimer; Note that P22 has no Dec, but its very close relative phage L does and L Dec binds to P22 capsids.	Tang et al., 2006
Dec	gp5	Dec occupies a subset of the quasi-equivalent local threefold positions on the shell	Tang et al., 2006