Sequence and functional analysis of an Escherichia coli DNA fragment able to complement pqqE and pqqF mutants from Methylobacterium organophilum

A 7361 kb fragment of E coli chromosomal DNA able to complement pqqE and pqqF mutants of Methylobacterium organophilum has been sequenced. Five open reading frames (ORF) have been identified. Four ORFs (102, 103, 106 and 107), belong to a single transcription unit. They are separated by a transcription termination site from a fifth ORF (ORF109). Polypeptides of 28, 85 and 82 kDa encoded by ORFs 102, 103 and 106 respectively were visualised in maxi-cell experiments. Both ORF106 and ORF107 are required for complementations of pqqE and pqqF mutants from M organophilum. The polypeptides encoded by ORFs102, 103 and 107 have no homologies with the products of pqq genes previously sequenced from Acinetobacter calcoaceticus, Klebsiella pneumoniae, and Methylobacterium extorquens AM1. The polypeptide encoded by ORF106 shows homology with the pqqF gene product of K pneumoniae, and seems to belong to a family of zinc proteases. The sequence of ORF109 is identical to the sequence of the gadB gene of E coli encoding for a glutamate decarboxylase.