title: Conformational changes induced by binding of bivalent cations to oncomodulin, a paravalbumin-like tumour protein.
abstract: When Mg2+ was added to rat oncomodulin, a paravalbumin-like tumour protein, changes in the c.d. spectrum and tyrosine fluorescence intensity were observed. The addition of Ca2+ resulted in even greater changes in these spectra. The fluorescence excitation spectra of apo- and Mg-oncomodulin were superimposable, whereas that of Ca-oncomodulin was markedly different. The u.v.-absorption spectrum of the Ca2+ form also showed major differences from those of the other two forms. These observations indicate that Ca2+ induced a significant and specific conformational change in the protein that was not observed on binding Mg2+. In contrast, the conformational change induced by either Mg2+ or Ca2+ was identical in the homologous rat parvalbumin. This Ca2+-specific conformational change may be the basis for oncomodulin's Ca2+-dependent protein/protein interaction.
mesh_terms: D000818:Animals; D002118:Calcium; D002135:Calcium-Binding Proteins; D002942:Circular Dichroism; D008274:Magnesium; D009363:Neoplasm Proteins; D011485:Protein Binding; D011487:Protein Conformation; D051381:Rats; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D014443:Tyrosine
chemical_list: D002135:Calcium-Binding Proteins; D009363:Neoplasm Proteins; C034733:oncomodulin; D014443:Tyrosine; D008274:Magnesium; D002118:Calcium