An unusual route to thermostability disclosed by the comparison of Thermus thermophilus and Escherichia coli inorganic pyrophosphatases

A1 Journal article (refereed)


Internal Authors/Editors


Publication Details

List of Authors: Salminen T, Teplyakov A, Kankare J, Cooperman BS, Lahti R, Goldman A
Publisher: CAMBRIDGE UNIV PRESS
Publication year: 1996
Journal: Protein Science
Journal acronym: PROTEIN SCI
Volume number: 5
Issue number: 6
Start page: 1014
End page: 1025
Number of pages: 12
ISSN: 0961-8368


Abstract

The structures of Escherichia coli soluble inorganic pyrophosphatase (E-PPase) and Thermus thermophilus soluble inorganic pyrophosphatase (T-PPase) have been compared to find the basis for the superior thermostability of T-PPase. Both enzymes are D-3 hexamers and crystallize in the same space group with very similar cell dimensions. Two rather small changes occur in the T-PPase monomer: a systematic removal of Ser residues and insertion of Arg residues, but only in the C-terminal part of the protein, and more long-range ion pairs from the C-terminal helix to the rest of the molecule. Apart from the first five residues, the three-dimensional structures of E-PPase and T-PPase monomers are very similar.The one striking difference, how;ever, is in the oligomeric interactions. In comparison with an E-PPase monomer, each T-PPase monomer is skewed by about 1 Angstrom in the xy plane, is 0.3 Angstrom closer to the center of the hexamer in the z direction, and is rotated by approximately 7 degrees about its center of gravity. Consequently, there are a number of additional hydrogen bond and ionic interactions, many of which form an interlocking network that covers all of the oligomeric surfaces. The change can also be seen in local distortions of three small loops involved in the oligomeric interfaces. The complex rigid-body motion has the effect that the hexamer is more tightly packed in T-PPase: the amount of surface area buried upon oligomerization increases by 16%. The change is sufficiently large to account for all of the increased thermostability of T-PPase over E-PPase and further supports the idea that bacterial PPases, most active as hexamers or tetramers, achieve a large measure of their stabilization through oligomerization. Rigid-body motions of entire monomers to produce tighter oligomers may be yet another way in which proteins can be made thermophilic.


Keywords

inorganic pyrophosphatase, Structural analysis, thermostability

Last updated on 2019-14-12 at 03:16