1JP7

Crystal Structure of 5'-deoxy-5'-methylthioadenosine phosphorylase

Summary for 1JP7

• Entry DOI: 10.2210/pdb1jp7/pdb
• Related: 1JDS 1JDT 1JDU 1JDV 1JDZ 1JE0 1JE1 1JPV
• Descriptor: 5'-deoxy-5'-methylthioadenosine phosphorylase, SULFATE ION (2 entities in total)
• Functional Keywords: alpha-beta protein, transferase
• Biological source: Sulfolobus solfataricus
• Total number of polymer chains: 3
• Total formula weight: 77578.56

Authors

Appleby, T.C.,Mathews, I.I.,Porcelli, M.,Cacciapuoti, G.,Ealick, S.E. (deposition date: 2001-08-01, release date: 2001-10-26, Last modification date: 2024-04-03)

Primary citation

Appleby, T.C.,Mathews, I.I.,Porcelli, M.,Cacciapuoti, G.,Ealick, S.E.
Three-dimensional structure of a hyperthermophilic 5'-deoxy-5'-methylthioadenosine phosphorylase from Sulfolobus solfataricus.
J.Biol.Chem., 276:39232-39242, 2001

PubMed Abstract: 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.

PubMed: 11489901
DOI: 10.1074/jbc.M105694200

Experimental method

X-RAY DIFFRACTION (1.8 Å)