Using the mini-Mu-duction technique, we cloned the malA regions from Escherichia coli K-12 and Klebsiella pneumoniae. A comparison of the structures of the cloned DNAs indicated that the malT, malP, and malQ genes, encoding the transcriptional activator of the maltose regulon, maltodextrin phosphorylase, and amylomaltase, respectively, are similarly organized in both species; malP and malQ constitute an operon divergent from the malT gene. We sequenced 1,200 nucleotides encompassing the beginnings of the malT and malP genes, their promoters, and the intergenic region. The DNA sequences from the two species were very different; the levels of homology ranged from 28 to 80%, depending on the region. The sequences of the coding regions and of elements known to be important for the functions of these two promoters in E. coli were well conserved between the two bacteria, whereas the sequence of the malT-malP intergenic region had totally diverged.