The iap gene in Escherichia coli is responsible for the isozyme conversion of alkaline phosphatase. We analyzed the 1,664-nucleotide sequence of a chromosomal DNA segment that contained the iap gene and its flanking regions. The predicted iap product contained 345 amino acids with an estimated molecular weight of 37,919. The 24-amino-acid sequence at the amino terminus showed features characteristic of a signal peptide. Two proteins of different sizes were identified by the maxicell method, one corresponding to the lap protein and the other corresponding to the processed product without the signal peptide. Neither the isozyme-converting activity nor labeled Iap proteins were detected in the osmotic-shock fluid of cells carrying a multicopy iap plasmid. The Iap protein seems to be associated with the membrane.

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Induction of the Escherichia coli SOS system increases the ability of the cell to perform DNA repair and mutagenesis.