A fragment of Methylobacter albus BG8 DNA containing mxaF (moxF), the gene encoding the alpha subunit of methanol dehydrogenase, was previously cloned using a fragment of mxaF from Methylobacterium extorquens AM1 as a probe (Stephens et al., J. Bacteriol. (1988) 170, 2063-2069). In this study we identified the 5' portion of mxaF of M. albus BG8 and sequenced a 1.7-kb region containing the 5' portion of mxaF and 1.5 kb of upstream DNA. The deduced N-terminal amino acid sequence of mxaF was found to have very high similarity to the previously sequenced mxaF genes. The region directly upstream of mxaF was cloned into a promoter probe vector (pGD500), and promoter activity was demonstrated when the fragment was present in the correct orientation with relation to the reporter gene (lacZ). Using reverse transcriptase, the transcription initiation start site was determined, which was separated from the translation initiation site by 190 nucleotides.