Structure of Escherichia coli inorganic pyrophosphatase at 2.2 angstrom resolution

A1 Originalartikel i en vetenskaplig tidskrift (referentgranskad)


Interna författare/redaktörer


Publikationens författare: Kankare J, Salminen T, Lahti R, Cooperman BS, Baykov AA, Goldman A
Förläggare: MUNKSGAARD INT PUBL LTD
Publiceringsår: 1996
Tidskrift: Acta Crystallographica Section D: Biological Crystallography
Tidskriftsakronym: ACTA CRYSTALLOGR D
Volym: 52
Artikelns första sida, sidnummer: 551
Artikelns sista sida, sidnummer: 563
Antal sidor: 13
ISSN: 0907-4449


Abstrakt

The refined crystal structures of hexameric soluble inorganic pyrophosphatase from E. coli (E-PPase) are reported to R factors of 18.7 and 18.3% at 2.15 and 2.2 Angstrom, respectively. The first contains one independent monomer; the other, two independent monomers, in an R32 unit cell. Because the E-PPase monomer is small with a large open active site, there are relatively few hydrophobic interactions that connect the active-site loops to the five-stranded twisted beta-barrel that is the hydrophobic core of the molecule. The active-site loops are, however, held in place by interactions between monomers around the threefold and twofold symmetry axes of the D-3 hexamer. Consequently, mutations of active-site residues (such as Glu20 and Lys104) often affect protein stability and oligomeric structure. Conversely, mutations of residues in the interface between monomers (such as His136 and His140) not only affect oligomeric structure but also affect active-site function. The effects of the H136Q and H140Q variants can be explained by the extended ionic interaction between H140, D143 and H136' of the neighbouring monomer. This interaction is further buttressed by an extensive hydrogen-bonding network that appears to explain why the E-PPase hexamer is so stable and also why the H136Q and H140Q variant proteins are less stable as hexamers.

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