Dataset Information

Ald of Mycobacterium tuberculosis encodes both the alanine dehydrogenase and the putative glycine dehydrogenase.

ABSTRACT: The putative glycine dehydrogenase of Mycobacterium tuberculosis catalyzes the reductive amination of glyoxylate to glycine but not the reverse reaction. The enzyme was purified and identified as the previously characterized alanine dehydrogenase. The Ald enzyme was expressed in Escherichia coli and had both pyruvate and glyoxylate aminating activities. The gene, ald, was inactivated in M. tuberculosis, which resulted in the loss of all activities. Both enzyme activities were found associated with the cell and were not detected in the extracellular filtrate. By using an anti-Ald antibody, the protein was localized to the cell membrane, with a smaller fraction in the cytosol. None was detected in the extracellular medium. The ald knockout strain grew without alanine or glycine and was able to utilize glycine but not alanine as a nitrogen source. Transcription of ald was induced when alanine was the sole nitrogen source, and higher levels of Ald enzyme were measured. Ald is proposed to have several functions, including ammonium incorporation and alanine breakdown.

SUBMITTER: Giffin MM

PROVIDER: S-EPMC3294785 | biostudies-literature | 2012 Mar

REPOSITORIES: biostudies-literature

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ald of Mycobacterium tuberculosis encodes both the alanine dehydrogenase and the putative glycine dehydrogenase.

Giffin Michelle M MM Modesti Lucia L Raab Ronald W RW Wayne Lawrence G LG Sohaskey Charles D CD

Journal of bacteriology 20111230 5

The putative glycine dehydrogenase of Mycobacterium tuberculosis catalyzes the reductive amination of glyoxylate to glycine but not the reverse reaction. The enzyme was purified and identified as the previously characterized alanine dehydrogenase. The Ald enzyme was expressed in Escherichia coli and had both pyruvate and glyoxylate aminating activities. The gene, ald, was inactivated in M. tuberculosis, which resulted in the loss of all activities. Both enzyme activities were found associated wi ...[more]

PMID: 22210765

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Project description:UnlabelledIn the presence of alanine, AldR, which belongs to the Lrp/AsnC family of transcriptional regulators and regulates ald encoding alanine dehydrogenase in Mycobacterium smegmatis, changes its quaternary structure from a homodimer to an octamer with an open-ring conformation. Four AldR-binding sites (O2, O1, O4, and O3) with a consensus sequence of GA/T-N2-NWW/WWN-N2-A/TC were identified upstream of the M. smegmatis ald gene by means of DNase I footprinting analysis. O2, O1, and O4 are required for the induction of ald expression by alanine, while O3 is directly involved in the repression of ald expression. In addition to O3, both O1 and O4 are also necessary for full repression of ald expression in the absence of alanine, due to cooperative binding of AldR dimers to O1, O4, and O3. Binding of a molecule of the AldR octamer to the ald control region was demonstrated to require two AldR-binding sites separated by three helical turns between their centers and one additional binding site that is in phase with the two AldR-binding sites. The cooperative binding of AldR dimers to DNA requires three AldR-binding sites that are aligned with a periodicity of three helical turns. The aldR gene is negatively autoregulated independently of alanine. Comparative analysis of ald expression of M. smegmatis and Mycobacterium tuberculosis in conjunction with sequence analysis of both ald control regions led us to suggest that the expression of the ald genes in both mycobacterial species is regulated by the same mechanism.ImportanceIn mycobacteria, alanine dehydrogenase (Ald) is the enzyme required both to utilize alanine as a nitrogen source and to grow under hypoxic conditions by maintaining the redox state of the NADH/NAD(+) pool. Expression of the ald gene was reported to be regulated by the AldR regulator that belongs to the Lrp/AsnC (feast/famine) family, but the underlying mechanism was unknown. This study revealed the regulation mechanism of ald in Mycobacterium smegmatis and Mycobacterium tuberculosis. Furthermore, a generalized arrangement pattern of cis-acting regulatory sites for Lrp/AsnC (feast/famine) family regulators is suggested in this study.

Dataset Information

Ald of Mycobacterium tuberculosis encodes both the alanine dehydrogenase and the putative glycine dehydrogenase.

Publications

ald of Mycobacterium tuberculosis encodes both the alanine dehydrogenase and the putative glycine dehydrogenase.

Similar Datasets

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