Structure of Thermotoga maritima stationary phase survival protein SurE: a novel acid phosphatase.
BACKGROUND
The rpoS, nlpD, pcm, and surE genes are among many whose expression is induced during the stationary phase of bacterial growth. rpoS codes for the stationary-phase RNA polymerase sigma subunit, and nlpD codes for a lipoprotein. The pcm gene product repairs damaged proteins by converting the atypical isoaspartyl residues back to L-aspartyls. The physiological and biochemical functions of surE are unknown, but its importance in stress is supported by the duplication of the surE gene in E. coli subjected to high-temperature growth. The pcm and surE genes are highly conserved in bacteria, archaea, and plants.


RESULTS
The structure of SurE from Thermotoga maritima was determined at 2.0 A. The SurE monomer is composed of two domains; a conserved N-terminal domain, a Rossman fold, and a C-terminal oligomerization domain, a new fold. Monomers form a dimer that assembles into a tetramer. Biochemical analysis suggests that SurE is an acid phosphatase, with an optimum pH of 5.5-6.2. The active site was identified in the N-terminal domain through analysis of conserved residues. Structure-based site-directed point mutations abolished phosphatase activity. T. maritima SurE intra- and intersubunit salt bridges were identified that may explain the SurE thermostability.


CONCLUSIONS
The structure of SurE provided information about the protein's fold, oligomeric state, and active site. The protein possessed magnesium-dependent acid phosphatase activity, but the physiologically relevant substrate(s) remains to be identified. The importance of three of the assigned active site residues in catalysis was confirmed by site-directed mutagenesis.
Zhang
R G
RG
Biosciences Division and Structural Biology Center, Argonne National Laboratory, 9700 South Cass Avenue, Building 202, Argonne, IL 60439, USA.
Skarina
T
T
Katz
J E
JE
Beasley
S
S
Khachatryan
A
A
Vyas
S
S
Arrowsmith
C H
CH
Clarke
S
S
Edwards
A
A
Joachimiak
A
A
Savchenko
A
A
D000595:Amino Acid Sequence; D020134:Catalytic Domain / Q000235:genetics; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D004789:Enzyme Activation; D008274:Magnesium / Q000494:pharmacology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D020124:Thermotoga maritima / Q000201:enzymology*
C446281:SurE acid phosphatase; D010744:Phosphoric Monoester Hydrolases; D008274:Magnesium