TABLE IX.

Protein–protein interaction of phages P2 and P4

Protein	Function	Interactions	Notes	References
P2–P2 proteins
gpC	Immunity repressor	Dimer	Y2H 3D structure	Eriksson et al., 2000; Massad et al., 2010
Cox	Transcriptional repressor, excisionase	Tetramer that can self-associate to octamers	In vitro; cross-linking and gel filtration	Eriksson and Haggard-Ljungquist, 2000
Int	Integrase	Dimer	In vitro; cross-linking Y2H	Frumerie et al., 2005
gpFI	Tail sheath	Polymer, six molecules per sheath striation	Electron microscopy	Lengyel et al., 1974
gpFII	Tail tube	Polymer, six molecules per tube striation	Electron microscopy	Lengyel et al., 1974
gpM	Small terminase subunit	Polymer, 8- to 10-fold ring	Biochemistry	Dokland, unpublished data
gpM	Small terminase subunit	gpP	Biochemistry	Bowden and Modrich, 1985
gpN	Major capsid protein	T=7 icosahedron (415 copies)	Cryo-EM and 3D reconstruction	Dokland et al., 1992
		gpO	Biochemistry	Chang et al., 2008, 2009
gpO	Internal scaffolding protein	Dimer	Biochemistry, chromatography	Chang et al., 2008, 2009
		gpN
gpP	Large terminase subunit	gpP	Biochemistry	Bowden and Modrich, 1985
gpQ	Connector, portal protein	Dodecameric ring	EM, crystallography	Doan and Dokland, 2007; Rishovd et al., 1994
gpT	Tape measure	gpFII (gpFI ?)	Inside tail tube
gpV	Tailspike	Tetramer	Sedimentation velocity and molecular mass determination	Haggard-Ljungquist et al., 1995; Kageyama et al., 2009
gpV	Tailspike	gpW, base plate component. Belongs to the T4 gene 25-like superfamily	Copurification	Haggard-Ljungquist et al., 1995
P2–other phage proteins
Tin	Block superinfection of T-even phages	T4 SSB protein (gp32)	Genetic evidence	Mosig et al., 1997
gpC	Immunity repressor	P4 anti-repressor ε	Genetic evidence. Y2H	Geisselsoder et al., 1981; Liu et al., 1998; Eriksson et al., 2000
gpN	Major capsid protein	P4 Sid; size determinator, external scaffold	Cryo-EM and 3D reconstruction	Marvik et al., 1995; Wang et al., 2000; Dokland et al., 2002
gpN	Major capsid protein	P4 Psu; polarity suppressor; decoration protein	Cryo-EM and 3D reconstruction	Dokland et al., 1993
P2–host proteins
gpB	Helicase loader.	E. coli helicase DnaB	Genetic evidence.	Sunshine et al., 1975; Funnell and Inman, 1983; Odegrip et al., 2000
	Required for lagging strand synthesis		Electron microscopy.
			In vitro binding.
Ogr	Transcriptional activator of late operons	E. coli RNA polymerase α C-terminal domain	Genetic evidence	Sunshine and Sauer, 1975; Fujiki et al., 1976; King et al., 1992; Ayers et al., 1994; Wood et al., 1997
P4–host proteins
Psu	Polarity suppressor; anti-terminator	Rho	Genetics; chemical cross-linking	Sauer et al., 1981; Pani et al., 2009
Delta	Transcriptional activator, contains two Ogr domains	E. coli RNA polymerase	Genetics; homology to Ogr	Julien et al., 1997