Interaction between caltropin and the C-terminal region of smooth muscle caldesmon.
Caltropin (CaT) binds caldesmon (CaD) in a Ca(2+)-dependent manner with an affinity higher than that of calmodulin (CaM). Photo-crosslinking between CaT and a benzophenone-labeled C-terminal CaD fragment (27K) results in a 35-kDa protein that corresponds to the 1:1 adduct between CaT and 27K. In the absence of Ca2+, no crosslinking is obtained. This result is similar to that obtained with CaM and 27K. The apparent affinity of CaM for GS17C, a CaM-binding peptide of CaD, is weakened by CaT, suggesting CaT competes with CaM for the peptide. In contrast to CaM, CaT does not induce changes in the tryptophan fluorescence of GS17C. Thus although the two Ca(2+)-binding proteins behave similarly, there are differences in their interactions with CaD.
Zhuang
S
S
Dept. of Biochemistry, Univ. of Alberta, Edmonton, Canada.
Mani
R S
RS
Kay
C M
CM
Wang
C L
CL
D000818:Animals; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002148:Calmodulin-Binding Proteins / Q000378:metabolism*; D002417:Cattle; D018797:Cell Cycle Proteins; D002645:Chickens; D009130:Muscle, Smooth / Q000378:metabolism*; D011485:Protein Binding; D011817:Rabbits; D000075383:S100 Calcium Binding Protein A6; D009418:S100 Proteins; D013050:Spectrometry, Fluorescence
D002135:Calcium-Binding Proteins; D002148:Calmodulin-Binding Proteins; D018797:Cell Cycle Proteins; D000075383:S100 Calcium Binding Protein A6; D009418:S100 Proteins; C489133:S100A6 protein, Gallus gallus