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Gene Review:

pemI - hypothetical protein

Escherichia coli

Masuda, Y. et al., Tsuchimoto, S. et al., Tsuchimoto, S. et al., Zhang, J. et al.

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Disease relevance of pemI

We found that the PemI amino acid sequence is homologous to two open reading frames from Escherichia coli called mazE and orf-83, which are located at 60 and 100 min on the chromosome, respectively [1].

High impact information on pemI

The pemI-pemK system is an addiction module present on plasmid R100 [2].
The pem locus is responsible for stable maintenance of plasmid R100 and consists of two genes, pemI and pemK [1].
The coexistence of the pem+ plasmid with a high-copy-number plasmid carrying the other open reading frame inhibited stabilization, and thus, the second open reading frame is a gene designated pemI, which encodes the inhibitor which might control the killing function of pemK [3].

Biological context of pemI

The low copy number plasmid R100 carries the pem region, consisting of two genes, pemI and pemK, which are required for stable maintenance of the plasmid [4].
This indicates that pemK and pemI cistrons form an operon, and that the expression of the operon is negatively regulated by its own products [4].
We cloned and sequenced these loci and found additional open reading frames, one downstream of each pemI homolog, both of which encode proteins homologous to PemK [1].
Plasmid R100 was found to have two genes, designated pemK and pemI, that were responsible for its stable inheritance during cell division [3].
This indicates that both PemI and PemK proteins bind to the promoter region to autoregulate their synthesis [4].

Regulatory relationships of pemI

Further studies reveal that PemK is a sequence-specific endoribonuclease that cleaves mRNAs to inhibit protein synthesis, whereas PemI blocks the endoribonuclease activity of PemK [2].

Analytical, diagnostic and therapeutic context of pemI

We then conducted a gel retardation assay in vitro and found that the two pem products, each of which was obtained as a tripartite protein (PemI-collagen-LacZ and PemK-collagen-LacZ), bound cooperatively to a specific fragment containing the proximal region of the pem operon [4].

References

chpA and chpB, Escherichia coli chromosomal homologs of the pem locus responsible for stable maintenance of plasmid R100. Masuda, Y., Miyakawa, K., Nishimura, Y., Ohtsubo, E. J. Bacteriol. (1993) [Pubmed]
Interference of mRNA function by sequence-specific endoribonuclease PemK. Zhang, J., Zhang, Y., Zhu, L., Suzuki, M., Inouye, M. J. Biol. Chem. (2004) [Pubmed]
Two genes, pemK and pemI, responsible for stable maintenance of resistance plasmid R100. Tsuchimoto, S., Ohtsubo, H., Ohtsubo, E. J. Bacteriol. (1988) [Pubmed]
Autoregulation by cooperative binding of the PemI and PemK proteins to the promoter region of the pem operon. Tsuchimoto, S., Ohtsubo, E. Mol. Gen. Genet. (1993) [Pubmed]

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