Prokaryotic calcium-binding protein of the calmodulin superfamily. Calcium binding to a Saccharopolyspora erythraea 20 kDa protein. |
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Authors: | N Bylsma T Drakenberg I Andersson P F Leadlay S Forsén |
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Affiliation: | Physical Chemistry 2, University of Lund, Sweden. |
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Abstract: | The EF-hand calcium-binding protein from Saccharopolyspora erythraea has been shown, using 113Cd NMR, to possess three Cd(2+)-ion binding sites. This indicates that of the four EF-hand motifs in the molecule, one (probably site 2) is unable to bind Cd(2+)-ions. Data from the titration of the protein with Ca2+, in the presence of Quin2, were fitted to a curve calculated on the assumption that the protein contains three high affinity Ca2+ binding sites, two of which (pK1 = 8.0, pK2 = 9.0) are strongly cooperative, and one single site (pK3 = 7.5). Preliminary 1H NMR experiments indicate marked structural changes upon Ca(2+)-binding. |
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