Binding of calcium ions and SNAP-25 to the hexa EF-hand protein secretagogin
Secretagogin is a hexa EF-hand protein, which has been identified as a novel potential tumour marker. In the present study, we show that secretagogin binds four Ca2+ ions (log K-1 = 7.1 +/- 0.4, log K-2 = 4.7 +/- 0.6, log K-3 = 3.6 +/- 0.7 and log K-4 = 4.6 +/- 0.6 in physiological salt buffers) with a [Ca2+](0.5) of approx. 25 mu M. The tertiary structure of secretagogin changes significantly upo