Calcium-regulated DNA Binding and Oligomerization of the Neuronal Calcium-sensing Protein, Calsenilin/DREAM/KChIP3

Masanori Osawa, Kit I. Tong, Christina Lilliehook, Wilma Wasco, Joseph D. Buxbaum, H.-Y. Mary Cheng, Josef M. Penninger, Mitsuhiko Ikura, James B. Ames
2001 Journal of Biological Chemistry  
Calsenilin/DREAM/KChIP3, a member of the recoverin branch of the EF-hand superfamily, interacts with presenilins, serves as a calcium-regulated transcriptional repressor, and interacts with A-type potassium channels. Here we report physicochemical characterization of calcium binding, oligomerization, and DNA binding of human calsenilin/DREAM/KChIP3. Equilibrium Ca 2؉ binding measurements indicate that the protein binds 3 Ca 2؉ with a dissociation constant of 14 M and a Hill coefficient of 0.7.
more » ... ynamic light scattering and size exclusion chromatography show that the Ca 2؉ -bound protein exists as a dimer at protein concentrations lower than 150 M and forms a tetramer at concentrations above 200 M. The Ca 2؉ -free protein is a tetramer in the concentration range 20 -450 M. Isothermal titration calorimetry and dynamic light scattering indicate that the Ca 2؉ -free protein tetramer binds endothermically (⌬H ‫؍‬ ؉25 kcal/mol) to four molecules of DNA derived from the downstream regulatory element (DRE) of either the prodynorphin or c-fos genes. One DRE molecule binds tightly to the protein with a dissociation constant (K d ) of 75 nM, and the other three bind more weakly (K d ‫؍‬ 640 nM). No significant DNA binding was observed for the Ca 2؉ -bound protein.
doi:10.1074/jbc.m105842200 pmid:11535596 fatcat:ekbrgrlrsvgxjiygid3r5zfkeq