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Cellular and Molecular Life Sciences: CMLS logoLink to Cellular and Molecular Life Sciences: CMLS
. 2008 Oct 16;65(22):3688–3697. doi: 10.1007/s00018-008-8502-7

Na+ binding to meizothrombin desF1

M E Papaconstantinou 1, P S Gandhi 1, Z Chen 1, A Bah 1, E Di Cera 1,
PMCID: PMC2662498  NIHMSID: NIHMS99179  PMID: 18854941

Abstract.

Meizothrombin is the physiologically active intermediate generated by a single cleavage of prothrombin at R320 to separate the A and B chains. Recent evidence has suggested that meizothrombin, like thrombin, is a Na+-activated enzyme. In this study we present the first X-ray crystal structure of human meizothrombin desF1 solved in the presence of the active site inhibitor PPACK at 2.1 Å resolution. The structure reveals a Na+ binding site whose architecture is practically identical to that of human thrombin. Stopped-flow measurements of Na+ binding to meizothrombin desF1 document a slow phase of fluorescence change with a k obs decreasing hyperbolically with increasing [Na+], consistent with the existence of three conformations in equilibrium, E*, E and E:Na+, as for human thrombin. Evidence that meizothrombin exists in multiple conformations provides valuable new information for studies of the mechanism of prothrombin activation.

Keywords. Thrombin, meizothrombin, allostery, linkage, Na+ binding

Footnotes

Received 15 August 2008; received after revision 15 September 2008; accepted 01 October 2008


Articles from Cellular and Molecular Life Sciences: CMLS are provided here courtesy of Springer

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