1QEZ

SULFOLOBUS ACIDOCALDARIUS INORGANIC PYROPHOSPHATASE: AN ARCHAEL PYROPHOSPHATASE.

Summary for 1QEZ

• Entry DOI: 10.2210/pdb1qez/pdb
• Descriptor: PROTEIN (INORGANIC PYROPHOSPHATASE), MAGNESIUM ION (3 entities in total)
• Functional Keywords: inorganic pyrophosphatase, thermostability, magnesium, hydrolase
• Biological source: Sulfolobus acidocaldarius
• Cellular location: Cytoplasm : P50308
• Total number of polymer chains: 6
• Total formula weight: 116563.50

Authors

Leppanen, V.-M.,Nummelin, H.,Hansen, T.,Lahti, R.,Schafer, G.,Goldman, A. (deposition date: 1999-04-06, release date: 1999-04-14, Last modification date: 2023-08-16)

Primary citation

Leppanen, V.M.,Nummelin, H.,Hansen, T.,Lahti, R.,Schafer, G.,Goldman, A.
Sulfolobus acidocaldarius inorganic pyrophosphatase: structure, thermostability, and effect of metal ion in an archael pyrophosphatase.
Protein Sci., 8:1218-1231, 1999

PubMed Abstract: The first crystal structure of an inorganic pyrophosphatase (S-PPase) from an archaebacterium, the thermophile Sulfolobus acidocaldarius, has been solved by molecular replacement and refined to an R-factor of 19.7% at 2.7 A. S-PPase is a D3 homohexameric protein with one Mg2+ per active site in a position similar to, but not identical with, the first activating metal in mesophilic pyrophosphatases (PPase). In mesophilic PPases, Asp65, Asp70, and Asp102 coordinate the Mg2+, while only Asp65 and Asp102 do in S-PPase, and the Mg2+ moves by 0.7 A. S-PPase may therefore be deactivated at low temperature by mispositioning a key metal ion. The monomer S-PPase structure is very similar to that of Thermus thermophilus (T-PPase) and Escherichia coli (E-PPase), root-mean-square deviations around 1 A/Calpha. But the hexamer structures of S- and T-PPase are more tightly packed and more similar to each other than they are to that of E-PPase, as shown by the increase in surface area buried upon oligomerization. In T-PPase, Arg116 creates an interlocking ionic network to both twofold and threefold related monomers; S-PPase has hydrophilic interactions to threefold related monomers absent in both E- and T-PPase. In addition, the thermostable PPases have about 7% more hydrogen bonds per monomer than E-PPase, and, especially in S-PPase, additional ionic interactions anchor the C-terminus to the rest of the protein. Thermostability in PPases is thus due to subtle improvements in both monomer and oligomer interactions.

PubMed: 10386872

Experimental method

X-RAY DIFFRACTION (2.7 Å)