This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Watson, R J Articles by Rastogi, V K Search for Related Content PubMed PubMed Citation Articles by Watson, R J Articles by Rastogi, V K

research-article

Cloning and nucleotide sequencing of Rhizobium meliloti aminotransferase genes: an aspartate aminotransferase required for symbiotic nitrogen fixation is atypical.

Plant Research Centre, Agriculture Canada, Ottawa, Ontario.

ABSTRACT

In Rhizobium meliloti, an aspartate aminotransferase (AspAT) encoded within a 7.3-kb HindIII fragment was previously shown to be required for symbiotic nitrogen fixation and aspartate catabolism (V. K. Rastogi and R.J. Watson, J. Bacteriol. 173:2879-2887, 1991). A gene coding for an aromatic aminotransferase located within an 11-kb HindIII fragment was found to complement the AspAT deficiency when overexpressed. The genes encoding these two aminotransferases, designated aatA and tatA, respectively, have been localized by subcloning and transposon Tn5 mutagenesis. Sequencing of the tatA gene revealed that it encodes a protein homologous to an Escherichia coli aromatic aminotransferase and most of the known AspAT enzymes. However, sequencing of the aatA gene region revealed two overlapping open reading frames, neither of which encoded an enzyme with homology to the typical AspATs. Polymerase chain reaction was used to selectively generate one of the candidate sequences for subcloning. The cloned fragment complemented the original nitrogen fixation and aspartate catabolism defects and was shown to encode an AspAT with the expected properties. Sequence analysis showed that the aatA protein has homology to AspATs from two thermophilic bacteria and the eukaryotic tyrosine aminotransferases. These aminotransferases form a distinct class in which only 13 amino acids are conserved in comparison with the well-known AspAT family. DNA homologous to the aatA gene was found to be present in Agrobacterium tumefaciens and other rhizobia but not in Klebsiella pneumoniae or E. coli.

This article has been cited by other articles:

• Lodwig, E., Kumar, S., Allaway, D., Bourdes, A., Prell, J., Priefer, U., Poole, P. (2004). Regulation of L-Alanine Dehydrogenase in Rhizobium leguminosarum bv. viciae and Its Role in Pea Nodules. J. Bacteriol. 186: 842-849 [Abstract] [Full Text]  
• Patriarca, E. J., Tate, R., Iaccarino, M. (2002). Key Role of Bacterial NH4+ Metabolism in Rhizobium-Plant Symbiosis. Microbiol. Mol. Biol. Rev. 66: 203-222 [Abstract] [Full Text]  
• Matsui, I., Matsui, E., Sakai, Y., Kikuchi, H., Kawarabayasi, Y., Ura, H., Kawaguchi, S.-i., Kuramitsu, S., Harata, K. (2000). The Molecular Structure of Hyperthermostable Aromatic Aminotransferase with Novel Substrate Specificity from Pyrococcus horikoshii. J. Biol. Chem. 275: 4871-4879 [Abstract] [Full Text]  
• Nobe, Y., Kawaguchi, S.-i., Ura, H., Nakai, T., Hirotsu, K., Kato, R., Kuramitsu, S. (1998). The Novel Substrate Recognition Mechanism Utilized by Aspartate Aminotransferase of the Extreme Thermophile Thermus thermophilus HB8. J. Biol. Chem. 273: 29554-29564 [Abstract] [Full Text]