*1.W.9. The Escherichia coli* Mu Phage Portal Protein 9 (PPP9) Family** The phage Mu protein forms the portal vertex of the capsid (Grimaud 1996). This portal plays critical roles in head assembly, genome packaging, neck/tail attachment, and genome ejection. The portal protein multimerizes as a single ring-shaped homododecamer arranged around a central channel (Grimaud and Toussaint 1998). and binds to the terminase subunits to form the packaging machine. It also acts as a linker between the capsid and tail and is required for attachment of the neck proteins to the capsid. The viral genome is injected through the host cell envelope using a cntractile tail mechanism (Morgan et al. 2002).
This family belongs to the Phage Portal Protein (PPP) Superfamily.
References:
Grimaud, R. (1996). Bacteriophage Mu head assembly. Virology 217: 200-210.
Grimaud, R. and A. Toussaint. (1998). Assembly of both the head and tail of bacteriophage Mu is blocked in Escherichia coli groEL and groES mutants. J. Bacteriol. 180: 1148-1153.
Morgan, G.J., G.F. Hatfull, S. Casjens, and R.W. Hendrix. (2002). Bacteriophage Mu genome sequence: analysis and comparison with Mu-like prophages in Haemophilus, Neisseria and Deinococcus. J. Mol. Biol. 317: 337-359.
Examples:
TC#	Name	Organismal Type	Example
1.W.9.1.1	Vortex phage mu portal protein of 512 aas		*PPP of E. coli* phage Mu**

1.W.9.1.10	Uncharacterized structural protein of 498 aas		*UP of Curvibacter* phage P26059A**

1.W.9.1.11	Portal protein of 472 aa		*PP of Arthrobacter* phage KBurrousTX**

1.W.9.1.12	DUF935 protein of 452 aas		DUF935 protein of Planctomycetes bacterium Pla85_3_4

1.W.9.1.13	Portal protein of 448 aas. The structure is known (PDB entries 4ZJN and 5NGD)		*PPP of Thermus* virus P74-26**

1.W.9.1.14	DUF935 family protein of 584 aas. This protein shows significant sequence similarity to members of 1.W.5, 1.W.7 as well as other members of 1.W.9.		DUF935 protein of Sandaracinus amylolyticus

1.W.9.1.15	DUF935 family protein of 429 aa		DUF935 family protein of Campylobacter corcagiensis

1.W.9.1.16	DUF935 family protein of 731 aas. This protein shows sequence similarity with TC#s 1.W.9.3.1 and 4.1.		DUF935 protein of Candidatus Atribacteria bacterium

1.W.9.1.2	The DUF935 family protein (phage portal protein) of 487 aas		DUF935 protein of Meiothermus phage MMP7

1.W.9.1.3	Uncharacterized protein of 401 aas		UP of Spirochaetia bacterium

1.W.9.1.4	DUF935 family protein of 1036 aa		DUF935 putative portal protein of Hymenobacter nivis

1.W.9.1.5	DUF935 family protein of 467 aa		DUF935 protein of Sulfurospirillum cavolei

1.W.9.1.6	DUF935 protein of 509 aas		DUF935 protein of Puniceicoccaceae bacterium

1.W.9.1.7	DUF935 protein of 416 aas		DUF935 protein of Treponema phagedenis

1.W.9.1.8	DUF935 protein of 617 aas		DUF935 protein of Desulfurellales bacterium

1.W.9.1.9	DUF935 famiy protein of 557 aas		DUF935 protein of Candidatus Atribacteria bacterium

Examples:
TC#	Name	Organismal Type	Example
1.W.9.2.1	Uncharacterized protein of 408 aas		UP of Chloroflexi bacterium

1.W.9.2.2	Uncharacterized protein of 433 aas		UP of Bryobacterales bacterium, Solibacterales bacterium (sediment metagenome)

Examples:
TC#	Name	Organismal Type	Example
1.W.9.3.1	Portal protein of 589 aas		*PP of Gordonia* phage RobinSparkles**

Examples:
TC#	Name	Organismal Type	Example
1.W.9.4.1	Uncharacterized protein of 340 aas		UP of Candidatus Rokubacteria bacterium (groundwater metagenome)