IDENTIFICATION OF A MEMBRANE-PROTEIN AND A TRUNCATED LYSR-TYPE REGULATOR ASSOCIATED WITH THE TOLUENE DEGRADATION PATHWAY IN PSEUDOMONAS-PUTIDA F1

A 3 kb DNA region upstream of the toluene degradation (rod) genes, tod FC1C2BADEGIH, in Pseudomonas putida F1 (PpF1) was sequenced. Two diver gently arranged open reading frames, todR and todX, were identified. A toluene-inducible promoter was localized in front of todX, and the tr anscription start point was mapped. This promoter is probably responsi ble for the expression of all tod structural genes. TodX was found to be a membrane protein. Its predicted amino acid sequence (453 residues ; M(r) 48 265) exhibits considerable similarity with the FadL protein of Escherichia coli, an outer membrane protein required for binding an d transport of long-chain fatty acids. An apparent function of TodX is likely to be involved in facilitating the delivery of exogenous tolue ne inside the PpF1 cells. The sequence of TodR (100 residues) exhibits extensive homology with the DNA-binding domain of transcriptional act ivators of the LysR family, but todR was found to have a negligible ro le in tod gene regulation.