Fluorescence Measurements of Ca2+ Binding to Domain VI of Calpain
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The Ca2+
binding properties of calpain are of great interest, both biochemically in the wider context of EF-hand proteins, and physiologically,
in the context of calpain regulation. There are two major parameters which one might wish to measure: the actual number of
binding sites (n) and the binding constants for Ca2+
. The latter is normally the macroscopic binding constant for Ca2+
of the molecule as a whole (Kd
), or the microscopic binding constants for each of the EF-hands, but for cooperative binding these are much more difficult
to measure. There is evidence of various kinds to suggest that Ca2+
binding causes conformational change in the whole molecule, and this forms the basis for measuring Ca2+
binding by means of changes in fluorescence.