Enzyme-substrate interactions revealed by the crystal structures of the archaeal Sulfolobus PTP-fold phosphatase and its phosphopeptide complexes.
The P-loop-containing protein phos-phatases are important regulators in signal transduction. These enzymes have structural and functional similarity with a conserved sequence of Dx(25-41)HCxxGxxR(T/S) essential for catalysis. The singular protein tyrosine phosphatase (PTP) from archaeal Sulfolobus solfataricus is one of the smallest known PTPs with extreme thermostability. Here, we report the crystal structure of this phosphatase and its complexes with two tyrosyl phosphopeptides A-(p)Y-R and N-K-(p)Y-G-N. The structure suggests the minimal structural motif of the PTP family, having two variable sequences inserted between the beta2-beta3 and beta3-beta4 strands, respectively. The phosphate of both phosphopeptide substrates is bound to the P-loop through several hydrogen bonds. Comparison of several phosphatase-substrate complexes revealed that Gln135 on the Q-loop has different modes of recognition toward phosphopeptides. The substrate specificity of SsoPTP is primarily localized at the phosphotyrosine, suggesting that this phosphatase may be a prototypical PTP.
Chu
Hsing-Mao
HM
Institute of Biochemical Sciences, National Taiwan University, Taipei 106, Taiwan.
Wang
Andrew H-J
AH
D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D008024:Ligands; D008958:Models, Molecular; D010748:Phosphopeptides / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D040681:Structural Homology, Protein; D013379:Substrate Specificity; D048229:Sulfolobus solfataricus / Q000201:enzymology* / Q000235:genetics
D008024:Ligands; D010748:Phosphopeptides; D017027:Protein Tyrosine Phosphatases