X-RAY CRYSTALLOGRAPHIC ANALYSIS OF THE INTERACTION OF 3-PHOSPHOGLYCERATE-KINASE (PGK) WITH ITS NUCLEOTIDE SUBSTRATES
Zoltán Kovári1, Zsolt Böcskei1,
Veronika Harmat1, Andrew May3,
Mária Vas2, Gábor Náray-Szabó1
1 ELTE, Dept. of Theoretical Chemistry. H-1518
Budapest POB: 32., Hungary
2 Institute of Enymology HAS H-1518 Budapest,
Hungary
3 Laboratory of Molecular Biophysics and Oxford
Centre for Molecular Sciences,University of Oxford, Oxford OX1
3QU, England
PGK is a ubiquitous enzyme, which produces ATP and 3-phosphoglycerate from ADP and 1,3-bis-phosphoglycerate glycolytic pathway. As other kinases, PGK can only convert nucleotides if they are in complexed form with metal, mostly with magnesium. The role of the metal ion in the reaction mechanism is one of the important problems which remains to be solved. As kinetic measurements have shown, PGK behaves in a different manner in the presence or in the absence of the metal ion [1].
To answer this question on a structural basis we have co-crystallized pig muscle PGK with ADP both in the presence and absence of magnesium ions. The resolution of the collected data were 1.8 and 2.0 Ĺ, respectively.
The phase problem was solved by the molecular replacement method, where the model was a horse muscle PGK [2] molecule.
The results show that there are two alternative conformations
of the adp-phosphate chain in the absence of metal, while only
one of them is present in the crystal form, if metal is present.