Premium
Heme‐CO as a probe of the conformational state of calmodulin
Author(s) -
Marden M.C.,
Leclerc L.,
Poyart C.
Publication year - 1990
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(90)81081-x
Subject(s) - calmodulin , heme , chemistry , histidine , ligand (biochemistry) , hemoglobin , calcium , hemeprotein , oxygen , carbon monoxide , kinetics , molecule , biophysics , stereochemistry , crystallography , photochemistry , biochemistry , catalysis , receptor , amino acid , biology , enzyme , organic chemistry , physics , quantum mechanics
The interaction of heme‐CO with calmodulin, in the presence of calcium, leads to a complex of four heme‐CO molecules per protein. No interaction was observed in the absence of calcium. The binding of heme‐CO to calmodulin was monitored by the shift in the Soret absorption band from 407 to 420 nm (bound form); the four sites are not spectrally identical. The ligand CO can be photodissociated from the calmodulin‐heme‐CO complex and the bimolecular recombination kinetics also indicate a heterogeneous mixture. The complex does not bind oxygen reversibly. As calmodulin has only one histidine, the hemes are apparently not bound by the iron atom as in hemoglobin, but are probably loosely associated ( K d =0.5 μM) in hydrophobic pockets which apparently open when the protein is activated by calcium.