Absorption and fluorescence spectroscopic studies of the Ca2(+)-dependent lipid binding protein p36: the annexin repeat as the Ca2+ binding site.
The existence of a single tryptophan residue in the protein p36, a member of a recently characterized family of Ca2+ binding proteins called annexins, is exploited to provide unique spectroscopic information on the annexin repeat motif and its role in Ca2+ binding. The differences in ultraviolet absorption and fluorescence excitation upon Ca2+ binding are interpreted solely in terms of this tryptophan, which, in view of the pronounced blue-shifts and the presence of vibronic structure, seems to reside in a highly nonpolar environment. The fluorescence emission from the protein is correspondingly blue-shifted, and it is found to transfer energy in resonance with Tb3+ absorption lines in the near-ultraviolet. This effect allows us to locate the Tb3+ and, by implication, the Ca2+ binding site to within ca. 8 A of the tryptophan residue.
Marriott
G
G
Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Goettingen, FRG.
Kirk
W R
WR
Johnsson
N
N
Weber
K
K
D000818:Animals; D017302:Annexins; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D002645:Chickens; D006801:Humans; D066298:In Vitro Techniques; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D013552:Swine; D013725:Terbium / Q000378:metabolism; D014364:Tryptophan / Q000737:chemistry
D017302:Annexins; D002135:Calcium-Binding Proteins; D013725:Terbium; D014364:Tryptophan; D002118:Calcium