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Differential Regulation of the Three Methanol Methyltransferase Isozymes in Methanosarcina acetivorans C2A

Arpita Bose, Matthew A. Pritchett, Michael Rother, and William W. Metcalf^*

Department of Microbiology, University of Illinois at Urbana-Champaign, B103 CLSL, 601 S. Goodwin, Urbana, Illinois 61801

Received 14 April 2006/ Accepted 30 July 2006

Genetic analysis of the three methanol-specific methyltransferase 1 operons (mtaCB1, mtaCB2, and mtaCB3) in Methanosarcina acetivorans led to the suggestion that each of them has a discrete function during growth on methanol, which might be reflected in differential gene regulation (Pritchett and Metcalf, Mol. Microbiol. 56:1183-1194, 2005). To test this suggestion, reporter gene fusions were constructed for each of the three operons, and their expression was examined under various growth conditions. Expression of the mtaCB1 and mtaCB2 fusions was 100-fold and 575-fold higher, respectively, in methanol-grown cells than in trimethylamine (TMA)-grown cells. The mtaCB3 fusion was expressed at low levels on methanol, TMA, and dimethylamine but was significantly upregulated on monomethylamine and acetate. When TMA- or acetate-grown cultures were shifted to methanol, the mtaCB1 fusion was expressed most highly during exponential phase, whereas the mtaCB2 fusion, although strongly induced prior to mtaCB1 expression, did not reach full expression levels until stationary phase. The mtaCB3 fusion was transiently expressed prior to entry into exponential phase during a TMA-to-methanol substrate shift experiment. When acetate-grown cells were shifted to medium containing both TMA and methanol, TMA utilization commenced prior to utilization of methanol; however, these two substrates were consumed simultaneously later in growth. Under these conditions expression of the mtaCB2 and mtaCB3 fusions was delayed, suggesting that methylamines may repress their expression.

Present address: University of California, San Diego, Center for Molecular Genetics 318, 9500 Gilman Drive, La Jolla, CA 92093-0634.

Present address: Institut für Mikrobiologie, Johann Wolfgang Goethe-Universität, Marie-Curie-Str. 9, D-60439 Frankfurt (Main), Germany.

This article has been cited by other articles:

• Bose, A., Pritchett, M. A., Metcalf, W. W. (2008). Genetic Analysis of the Methanol- and Methylamine-Specific Methyltransferase 2 Genes of Methanosarcina acetivorans C2A. J. Bacteriol. 190: 4017-4026 [Abstract] [Full Text]