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Thermophile-specific proteins: the gene product of aq_1292 from Aquifex aeolicus is an NTPase.

Klinger C, Rossbach M, Howe R, Kaufmann M - BMC Biochem. (2003)

Bottom Line: The enzyme is resistant to limited proteolysis suggesting that it consists of a single domain.Although THEP1s are annotated as "predicted nucleotide kinases" we could not confirm such an activity experimentally.Since aaTHEP1 is the first member of COG1618 that is characterized biochemically and functional information about one member of a COG may be transferred to the entire COG, we conclude that COG1618 proteins are a family of thermophilic NTPases.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute for Neurobiochemistry, The Protein Chemistry Group, Witten/Herdecke University, Stockumer Str 10, 58448 Witten, Germany. cklinger@uni-wh.de

ABSTRACT

Background: To identify thermophile-specific proteins, we performed phylogenetic patterns searches of 66 completely sequenced microbial genomes. This analysis revealed a cluster of orthologous groups (COG1618) which contains a protein from every thermophile and no sequence from 52 out of 53 mesophilic genomes. Thus, COG1618 proteins belong to the group of thermophile-specific proteins (THEPs) and therefore we here designate COG1618 proteins as THEP1s. Since no THEP1 had been analyzed biochemically thus far, we characterized the gene product of aq_1292 which is THEP1 from the hyperthermophilic bacterium Aquifex aeolicus (aaTHEP1).

Results: aaTHEP1 was cloned in E. coli, expressed and purified to homogeneity. At a temperature optimum between 70 and 80 degrees C, aaTHEP1 shows enzymatic activity in hydrolyzing ATP to ADP + Pi with kcat = 5 x 10(-3) s(-1) and Km = 5.5 x 10(-6) M. In addition, the enzyme exhibits GTPase activity (kcat = 9 x 10(-3) s(-1) and Km= 45 x 10(-6) M). aaTHEP1 is inhibited competitively by CTP, UTP, dATP, dGTP, dCTP, and dTTP. As shown by gel filtration, aaTHEP1 in its purified state appears as a monomer. The enzyme is resistant to limited proteolysis suggesting that it consists of a single domain. Although THEP1s are annotated as "predicted nucleotide kinases" we could not confirm such an activity experimentally.

Conclusion: Since aaTHEP1 is the first member of COG1618 that is characterized biochemically and functional information about one member of a COG may be transferred to the entire COG, we conclude that COG1618 proteins are a family of thermophilic NTPases.

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ATP hydrolysis is inhibited by GTP. Inhibition of aaTHEP1 catalyzed ATP hydrolysis by GTP. Each data point represents the mean ± SD of two independent measurements. 0.5 μg of purified aaTHEP1 were used for each assay in 25 μl buffer.
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Figure 8: ATP hydrolysis is inhibited by GTP. Inhibition of aaTHEP1 catalyzed ATP hydrolysis by GTP. Each data point represents the mean ± SD of two independent measurements. 0.5 μg of purified aaTHEP1 were used for each assay in 25 μl buffer.

Mentions: Competition experiments demonstrated that all nucleosidetriphosphates inhibit aaTHEP1 in hydrolyzing ATP. The data points fit to a model for competitive inhibition. As an example, inhibition by GTP is shown in figure 8. With the exception of GTP and dGTP, the Ki-values of all nucleotides are approximately in a similar range as the Km for ATP (table 3). Whereas GDP also inhibits ATP-hydrolysis, GMP, AMP, and UMP show no inhibition (figures 4 and 5).


Thermophile-specific proteins: the gene product of aq_1292 from Aquifex aeolicus is an NTPase.

Klinger C, Rossbach M, Howe R, Kaufmann M - BMC Biochem. (2003)

ATP hydrolysis is inhibited by GTP. Inhibition of aaTHEP1 catalyzed ATP hydrolysis by GTP. Each data point represents the mean ± SD of two independent measurements. 0.5 μg of purified aaTHEP1 were used for each assay in 25 μl buffer.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC222928&req=5

Figure 8: ATP hydrolysis is inhibited by GTP. Inhibition of aaTHEP1 catalyzed ATP hydrolysis by GTP. Each data point represents the mean ± SD of two independent measurements. 0.5 μg of purified aaTHEP1 were used for each assay in 25 μl buffer.
Mentions: Competition experiments demonstrated that all nucleosidetriphosphates inhibit aaTHEP1 in hydrolyzing ATP. The data points fit to a model for competitive inhibition. As an example, inhibition by GTP is shown in figure 8. With the exception of GTP and dGTP, the Ki-values of all nucleotides are approximately in a similar range as the Km for ATP (table 3). Whereas GDP also inhibits ATP-hydrolysis, GMP, AMP, and UMP show no inhibition (figures 4 and 5).

Bottom Line: The enzyme is resistant to limited proteolysis suggesting that it consists of a single domain.Although THEP1s are annotated as "predicted nucleotide kinases" we could not confirm such an activity experimentally.Since aaTHEP1 is the first member of COG1618 that is characterized biochemically and functional information about one member of a COG may be transferred to the entire COG, we conclude that COG1618 proteins are a family of thermophilic NTPases.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute for Neurobiochemistry, The Protein Chemistry Group, Witten/Herdecke University, Stockumer Str 10, 58448 Witten, Germany. cklinger@uni-wh.de

ABSTRACT

Background: To identify thermophile-specific proteins, we performed phylogenetic patterns searches of 66 completely sequenced microbial genomes. This analysis revealed a cluster of orthologous groups (COG1618) which contains a protein from every thermophile and no sequence from 52 out of 53 mesophilic genomes. Thus, COG1618 proteins belong to the group of thermophile-specific proteins (THEPs) and therefore we here designate COG1618 proteins as THEP1s. Since no THEP1 had been analyzed biochemically thus far, we characterized the gene product of aq_1292 which is THEP1 from the hyperthermophilic bacterium Aquifex aeolicus (aaTHEP1).

Results: aaTHEP1 was cloned in E. coli, expressed and purified to homogeneity. At a temperature optimum between 70 and 80 degrees C, aaTHEP1 shows enzymatic activity in hydrolyzing ATP to ADP + Pi with kcat = 5 x 10(-3) s(-1) and Km = 5.5 x 10(-6) M. In addition, the enzyme exhibits GTPase activity (kcat = 9 x 10(-3) s(-1) and Km= 45 x 10(-6) M). aaTHEP1 is inhibited competitively by CTP, UTP, dATP, dGTP, dCTP, and dTTP. As shown by gel filtration, aaTHEP1 in its purified state appears as a monomer. The enzyme is resistant to limited proteolysis suggesting that it consists of a single domain. Although THEP1s are annotated as "predicted nucleotide kinases" we could not confirm such an activity experimentally.

Conclusion: Since aaTHEP1 is the first member of COG1618 that is characterized biochemically and functional information about one member of a COG may be transferred to the entire COG, we conclude that COG1618 proteins are a family of thermophilic NTPases.

Show MeSH
Related in: MedlinePlus