PDBsum entry 2a8y

Transferase

PDB id: 2a8y

Contents

Protein chains

(+ 6 more) 263 a.a.

Ligands

SO4 ×24

MTA ×12

Waters ×3405

References listed in PDB file

Key reference

Title

The crystal structure of 5'-Deoxy-5'-Methylthioadenosine phosphorylase ii from sulfolobus solfataricus, A thermophilic enzyme stabilized by intramolecular disulfide bonds.

Authors

Y.Zhang, M.Porcelli, G.Cacciapuoti, S.E.Ealick.

Ref.

J Mol Biol, 2006, 357, 252-262. [DOI no: 10.1016/j.jmb.2005.12.040]

PubMed id

16414070

Abstract

The crystal structure of Sulfolobus solfataricus 5'-deoxy-5'-methylthioadenosine phosphorylase II (SsMTAPII) in complex with 5'-deoxy-5'-methylthioadenosine (MTA) and sulfate was determined to 1.45A resolution. The hexameric structure of SsMTAPII is a dimer-of-trimers with one active site per monomer. The oligomeric assembly of the trimer and the monomer topology of SsMTAPII are almost identical with trimeric human 5'-deoxy-5'-methylthioadenosine phosphorylase (hMTAP). SsMTAPII is the first reported hexameric member in the trimeric class of purine nucleoside phosphorylase (PNP) from Archaea. Unlike hMTAP, which is highly specific for MTA, SsMTAPII also accepts adenosine as a substrate. The residues at the active sites of SsMTAPII and hMTAP are almost identical. The broad substrate specificity of SsMTAPII may be due to the flexibility of the C-terminal loop. SsMTAPII is extremely thermoactive and thermostable. The three-dimensional structure of SsMTAPII suggests that the unique dimer-of-trimers quaternary structure, a CXC motif at the C terminus, and two pairs of intrasubunit disulfide bridges may play an important role in its thermal stability.

Figure 2.
Figure 2. Structure of the SsMTAPII subunit. (a) A ribbon diagram representing the secondary structural elements in the SsMTAPII subunit (a helices, blue; b strands, green). The substrate MTA and sulfate are shown in ball-and-stick representation. The disordered loop composed of residues 255-261 is shown as a dotted line. (b) Topology diagram. The a helices are shown as blue rectangles, and the b strands are shown as green arrows. Each secondary structural element is labeled in its center with its designator and with its beginning and ending sequence number.

Figure 5.
Figure 5. Schematic representation of the SsMTAPII active site. Residues of SsMTAPII are shown in black boxes. Residues in red boxes identify structurally equivalent residues in human MTAP. Residues in blue boxes represent structurally equivalent residues in human PNP. An asterisk designates residues from the neighboring subunit. Key hydrogen bonds are indicated by broken lines with the corresponding donor-acceptor distance labeled.

The above figures are reprinted by permission from Elsevier: J Mol Biol (2006, 357, 252-262) copyright 2006.