Three-dimensional structure of a hyperthermophilic 5'-deoxy-5'-methylthioadenosine phosphorylase from Sulfolobus solfataricus.Appleby, T.C., Mathews, I.I., Porcelli, M., Cacciapuoti, G., Ealick, S.E.
(2001) J.Biol.Chem. 276: 39232-39242
- PubMed: 11489901
- DOI: 10.1074/jbc.M105694200
- Primary Citation of Related Structures:
- PubMed Abstract:
- Purification and characterization of extremely thermophilic and thermostable 5'-methylthioadenosine phosphorylase from the archaeon Sulfolobus solfataricus. Purine nucleoside phosphorylase activity and evidence for intersubunit disulfide bonds
Cacciapuoti, G.,Porcelli, M.,Bertoldo, C.,De Rosa, M.,Zappia, V.
(1994) J.Biol.Chem. 269: 24762
- Three-Dimensional Structure of Human Erythrocytic Purine Nucleoside Phosphorylase At 3.2 Resolution
Ealick, S.E.,Rule, S.A.,Carter, D.C.,Greenhough, T.J.,Babu, Y.S.
(1990) J.Biol.Chem. 265: 1812
- The structure of human 5'-deoxy-5'-methylthioadenosine phosphorylase at 1.7 resolution provides insights into substrate binding and catalysis
Appleby, T.C.,Erion, M.D.,Ealick, S.E.
(1999) Structure 7: 629
The structure of 5'-deoxy-5'-methylthioadenosine phosphorylase from Sulfolobus solfataricus (SsMTAP) has been determined alone, as ternary complexes with sulfate plus substrates 5'-deoxy-5'-methylthioadenosine, adenosine, or guanosine, or with the no ...
The structure of 5'-deoxy-5'-methylthioadenosine phosphorylase from Sulfolobus solfataricus (SsMTAP) has been determined alone, as ternary complexes with sulfate plus substrates 5'-deoxy-5'-methylthioadenosine, adenosine, or guanosine, or with the noncleavable substrate analog Formycin B and as binary complexes with phosphate or sulfate alone. The structure of unliganded SsMTAP was refined at 2.5-A resolution and the structures of the complexes were refined at resolutions ranging from 1.6 to 2.0 A. SsMTAP is unusual both for its broad substrate specificity and for its extreme thermal stability. The hexameric structure of SsMTAP is similar to that of purine-nucleoside phosphorylase (PNP) from Escherichia coli, however, only SsMTAP accepts 5'-deoxy-5'-methylthioadenosine as a substrate. The active site of SsMTAP is similar to that of E. coli PNP with 13 of 18 nearest residues being identical. The main differences are at Thr(89), which corresponds to serine in E. coli PNP, and Glu(163), which corresponds to proline in E. coli PNP. In addition, a water molecule is found near the purine N-7 position in the guanosine complex of SsMTAP. Thr(89) is near the 5'-position of the nucleoside and may account for the ability of SsMTAP to accept either hydrophobic or hydrophilic substituents in that position. Unlike E. coli PNP, the structures of SsMTAP reveal a substrate-induced conformational change involving Glu(163). This residue is located at the interface between subunits and swings in toward the active site upon nucleoside binding. The high-resolution structures of SsMTAP suggest that the transition state is stabilized in different ways for 6-amino versus 6-oxo substrates. SsMTAP has optimal activity at 120 degrees C and retains full activity after 2 h at 100 degrees C. Examination of the three-dimensional structure of SsMTAP suggests that unlike most thermophilic enzymes, disulfide linkages play a key in role in its thermal stability.
Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA.