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. Study holds ProTherm entries: 6730, 6731, 6732, 6733, 6734, 6735, 6736, 6737 Extra Details: additive : EDTA(5 mM),
Submitter: Connie Wang
Submission Date: April 24, 2018, 8:32 p.m.
|Number of data points||8|
|Proteins||Inorganic pyrophosphatase ; Inorganic pyrophosphatase ; Inorganic pyrophosphatase ; Inorganic pyrophosphatase ; Inorganic pyrophosphatase ; Inorganic pyrophosphatase|
|Assays/Quantities/Protocols||Experimental Assay: Tm ionic:MgCl2: 5 mM, details:Additives ; Experimental Assay: Tm details:Additives EDTA (5 mM),, ionic::|
|Libraries||Mutations for sequence MKLSPGKNAPDVVNVLVEIPQGSNIKYEYDDEEGVIKVDRVLYTSMNYPFNYGFIPGTLEEDGDPLDVLVITNYQLYPGSVIEVRPIGILYMKDEEGEDAKIVAVPKDKTDPSFSNIKDINDLPQATKNKIVHFFEHYKELEPGKYVKISGWGSATEAKNRIQLAIKRVSGGQ ; Mutations for sequence SLLNVPAGKDLPEDIYVVIEIPANADPIKYEIDKESGALFVDRFMSTAMFYPCNYGYINHTLSLDGDPVDVLVPTPYPLQPGSVIRCRPVGVLKMTDEAGEDAKLVAVPHSKLSKEYDHIKDVNDLPELLKAQIAHFFEHYKDLEKGKWVKVEGWENAEAAKAEIVASFERAKNK ; Mutations for sequence ANLKSLPVGDKAPEVVHMVIEVPRGSGNKYEYDPDLGAIKLDRVLPGAQFYPGDYGFIPSTLAEDGDPLDGLVLSTYPLLPGVVVEVRVVGLLLMEDEKGGDAKVIGVVAEDQRLDHIQDIGDVPEGVKQEIQHFFETYKALEAKKGKWVKVTGWRDRKAALEEVRACIARYKG|