1.W.5.  The (Lambda) Phage Portal Protein 5 (PPP5) Family

The Escherichia phage lambda (Bacteriophage lambda) portal protein forms the portal vertex of the capsid (Kochan and Murialdo 1983). 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 (Kochan et al. 1984). It binds to the terminase subunits to form the packaging machine (Yeo and Feiss 1995).

This family belongs to the Phage Portal Protein (PPP) Superfamily.



Kochan, J. and H. Murialdo. (1983). Early intermediates in bacteriophage lambda prohead assembly. II. Identification of biologically active intermediates. Virology 131: 100-115.

Kochan, J., J.L. Carrascosa, and H. Murialdo. (1984). Bacteriophage lambda preconnectors. Purification and structure. J. Mol. Biol. 174: 433-447.

Yeo, A. and M. Feiss. (1995). Specific interaction of terminase, the DNA packaging enzyme of bacteriophage lambda, with the portal protein of the prohead. J. Mol. Biol. 245: 141-150.


TC#NameOrganismal TypeExample

The E. coli phage lambda portal protein (PPP) of 533 aas.  See family description for the characteristics of this protein.

PPP of E. coli phage lambda


Phage portal protein of 552 aa

PPP of Pseudomonas fluorescens


Phage portal protein [ of 528 aas and possibly C-terminal TMSs.

PPP of Bradyrhizobium sp. RP6


Phage portal protein of 497 aa

PPP of Pseudomethylobacillus aquaticus


Phage portal protein of 502 aas

PPP of Clostridium symbiosum


Phage portal protein of 454 aas

PPP of Sulfitobacter guttiformis


Phage portal protein of 473 aas

PPP of Planctomycetes bacterium (freshwater metagenome)


Phage portal protein of 599 aas

PPP of Candidatus Pacearchaeota archaeon (marine metagenome)


Phage portal protein of 570 aas.  This protein is homologous to protein in TC subclass 1.W.7.8.

PPP of Mailhella massiliensis