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Superinfection Immunity Protein

| posted 25 Jan, 2018 14:28
I am working with gene 72 from Niza, which is an A1 Mycobacteriophage. None of the phagesdb genes show a function but the top HHPred match is to pfam 14373, which is an Immunity Superfection protein based on the E.coli T4 gene described in J. Virol 1989 63:3472-8. Abstract below:
"The immunity (imm) gene of the Escherichia coli bacteriophage T4 effects exclusion of phage superinfecting cells already infected with T4. A candidate for this gene was placed under the control of the lac regulatory elements in a pUC plasmid. DNA sequencing revealed the presence of an open reading frame encoding a very lipophilic 83-residue (or 73-residue, depending on the unknown site of translation initiation) polypeptide which most likely represents a plasma membrane protein. This gene could be identified as the imm gene because expression from the plasmid caused exclusion of T4 and because interruption of the gene in the phage genome resulted in a phage no longer effecting superinfection immunity. It was found that the fraction of phage which was excluded upon infection of cells possessing the plasmid-encoded Imm protein ejected only about one-half of their DNA. Therefore, the Imm protein inhibited, directly or indirectly, DNA ejection."

The pfam14373 description is: "This family includes the E. coli bacteriophage T4 superinfection immunity (imm) protein. When E. coli is sequentially infected with two T-even type bacteriophage the DNA of the superinfecting phage is excluded from the host, into the periplasmic space. The immunity protein plays a role in this process."

Looking at Niza-72, the TMHMM predicts three transmembrane domains that covers 71 residues. The total length of the T4 protein is 76 amino acids and Niza-72 is 104 residues.

Finally, NCBI has chosen to recently add the pfam14373 region note to all of the top BLAST hits to Niza-72.

A decision for inclusion or exclusion of "superinfection immunity protein" in the accepted function list needs to be made since all future annotators of this Cluster A1 protein will want to include this as a function. It looks like Acinetobacter Baumannii (WP_062937363) has already included it as a function.

I didn't attach a DNA Master file since it is readily available on PECAAN.

| posted 06 Mar, 2018 21:11
Sorry, I don't think we are putting this one in any time soon. There are too many different types of unrelated proteins that could provide a similar effect. For now, stick to membrane protein. once we start getting a better handle on the proteins and their classes, maybe we can come up with something more detailed.
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