The thrH Gene Product of Pseudomonas aeruginosa Is a Dual Activity Enzyme with a Novel Phosphoserine:Homoserine Phosphotransferase Activity

The thrH gene product of Pseudomonas aeruginosa has been shown to complement both homoserine kinase (thrB gene product) and phosphoserine phosphatase (serB gene product) activities in vivo. Sequence comparison has revealed that ThrH is related to phosphoserine phosphatases (PSP, EC 3.1.3.3) and belo...

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Bibliographic Details
Published in:The Journal of biological chemistry 2004-03, Vol.279 (13), p.13166-13173
Main Authors: Singh, S. Kumar, Yang, Kun, Karthikeyan, Subramanian, Huynh, Tu, Zhang, Xuejun, Phillips, Margaret A., Zhang, Hong
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Bacterial Proteins - genetics
Bacterial Proteins - physiology
Binding Sites
Catalytic Domain
Chromatography, High Pressure Liquid
Cloning, Molecular
Crystallography, X-Ray
Kinetics
Models, Chemical
Models, Molecular
Molecular Sequence Data
Phosphoric Monoester Hydrolases - metabolism
Phosphotransferases (Alcohol Group Acceptor) - genetics
Phosphotransferases (Alcohol Group Acceptor) - metabolism
Phosphotransferases (Alcohol Group Acceptor) - physiology
Phosphotransferases - metabolism
Protein Binding
Protein Conformation
Protein Structure, Secondary
Protein Structure, Tertiary
Pseudomonas aeruginosa
Sequence Homology, Amino Acid
Ultraviolet Rays
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Summary:The thrH gene product of Pseudomonas aeruginosa has been shown to complement both homoserine kinase (thrB gene product) and phosphoserine phosphatase (serB gene product) activities in vivo. Sequence comparison has revealed that ThrH is related to phosphoserine phosphatases (PSP, EC 3.1.3.3) and belongs to the l-2-haloacid dehalogenase-like protein superfamily. We have solved the crystal structures of ThrH in the apoform and in complex with a bound product phosphate. The structure confirms an overall fold similar to that of PSP. Most of the catalytic residues of PSP are also conserved in ThrH, suggesting that similar catalytic mechanisms are used by both enzymes. Spectrophotometry-based in vitro assays show that ThrH is indeed a phosphoserine phosphatase with a Km of 0.207 mm and kcat of 13.4 min-1, comparable with those of other PSPs. More interestingly, using high pressure liquid chromatography-based assays, we have demonstrated that ThrH is able to further transfer the phosphoryl group to homoserine using phosphoserine as the phosphoryl group donor, indicating that ThrH has a novel phosphoserine:homoserine phosphotransferase activity.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M311393200