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Journal of Bacteriology, August 2005, p. 5719-5722, Vol. 187, No. 16
0021-9193/05/$08.00+0     doi:10.1128/JB.187.16.5719-5722.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Rickettsial metK-Encoded Methionine Adenosyltransferase Expression in an Escherichia coli metK Deletion Strain

Lonnie O. Driskell, Aimee M. Tucker, Herbert H. Winkler, and David O. Wood*

Department of Microbiology and Immunology, Laboratory of Molecular Biology, University of South Alabama College of Medicine, Mobile, Alabama 36688

Received 14 April 2005/ Accepted 31 May 2005

The obligate intracellular bacterium Rickettsia prowazekii has recently been shown to transport the essential metabolite S-adenosylmethionine (SAM). The existence of such a transporter would suggest that the metK gene, coding for the enzyme that synthesizes SAM, is unnecessary for rickettsial growth. Genome sequencing has revealed that this is the case for the metK genes of the spotted fever group and the Madrid E strain of R. prowazekii, which contain recognizable inactivating mutations. However, several strains of the typhus group rickettsiae possess metK genes lacking obvious mutations. In order to determine if these genes code for a product that retains MAT function, an Escherichia coli metK deletion mutant was constructed in which individual rickettsial metK genes were tested for the ability to complement the methionine adenosyltransferase deficiency. Both the R. prowazekii Breinl and R. typhi Wilmington metK genes complemented at a level comparable to that of an E. coli metK control, demonstrating that the typhus group rickettsiae have the capability of synthesizing as well as transporting SAM. However, the appearance of mutations that affect the function of the metK gene products (a stop codon in the Madrid E strain and a 6-bp deletion in the Breinl strain) provides experimental support for the hypothesis that these typhus group genes, like the more degenerate spotted fever group orthologs, are in the process of gene degradation.

* Corresponding author. Mailing address: Department of Microbiology and Immunology, Laboratory of Molecular Biology, University of South Alabama, Mobile, AL 36688-0002. Phone: (251) 460-6324. Fax: (251) 460-7269. E-mail: dowood{at}jaguar1.usouthal.edu.

Journal of Bacteriology, August 2005, p. 5719-5722, Vol. 187, No. 16
0021-9193/05/$08.00+0     doi:10.1128/JB.187.16.5719-5722.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Audia, J. P., Winkler, H. H. (2006). Study of the Five Rickettsia prowazekii Proteins Annotated as ATP/ADP Translocases (Tlc): Only Tlc1 Transports ATP/ADP, While Tlc4 and Tlc5 Transport Other Ribonucleotides.. J. Bacteriol. 188: 6261-6268 [Abstract] [Full Text]  


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