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Journal of Bacteriology, April 2009, p. 2033-2041, Vol. 191, No. 7
0021-9193/09/$08.00+0     doi:10.1128/JB.01591-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

In Vitro Characterization of the Enzyme Properties of the Phospholipid N-Methyltransferase PmtA from Agrobacterium tumefaciens{triangledown}

Meriyem Aktas and Franz Narberhaus*

Microbial Biology, Ruhr-University, Bochum, Germany

Received 10 November 2008/ Accepted 20 January 2009

Agrobacterium tumefaciens requires phosphatidylcholine (PC) in its membranes for plant infection. The phospholipid N-methyltransferase PmtA catalyzes all three transmethylation reactions of phosphatidylethanolamine (PE) to PC via the intermediates monomethylphosphatidylethanolamine (MMPE) and dimethylphosphatidylethanolamine (DMPE). The enzyme uses S-adenosylmethionine (SAM) as the methyl donor, converting it to S-adenosylhomocysteine (SAH). Little is known about the activity of bacterial Pmt enzymes, since PC biosynthesis in prokaryotes is rare. In this article, we present the purification and in vitro characterization of A. tumefaciens PmtA, which is a monomeric protein. It binds to PE, the intermediates MMPE and DMPE, the end product PC, and phosphatidylglycerol (PG) and phosphatidylinositol. Binding of the phospholipid substrates precedes binding of SAM. We used a coupled in vitro assay system to demonstrate the enzymatic activity of PmtA and to show that PmtA is inhibited by the end products PC and SAH and the antibiotic sinefungin. The presence of PG stimulates PmtA activity. Our study provides insights into the catalysis and control of a bacterial phospholipid N-methyltransferase.

* Corresponding author. Mailing address: Lehrstuhl für Biologie der Mikroorganismen, Fakultät für Biologie und Biotechnologie, Ruhr-Universität Bochum, Universitätsstrasse 150, NDEF 06/783, D-44780 Bochum, Germany. Phone: 49 (234) 322 3100. Fax: 49 (234) 321 4620. E-mail: franz.narberhaus{at}rub.de.

{triangledown} Published ahead of print on 30 January 2009.

Journal of Bacteriology, April 2009, p. 2033-2041, Vol. 191, No. 7
0021-9193/09/$08.00+0     doi:10.1128/JB.01591-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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