Oncomodulin and parvalbumin. A comparison of their interactions with europium ion.
The 7F0----5D0 transition of Eu3+ was used to probe the metal-binding domains of rat oncomodulin and rat parvalbumin. Two distinct differences between the two proteins were observed. The first relates to the pH-dependent behavior of their 7F0----5D0 spectra, a phenomenon noted previously for other paravalbumins. In the case of rat parvalbumin, the spectral features associated with both metal-binding sites titrate concomitantly (pK alpha = 8.2); however, in the case of oncomodulin, the two sites titrate sequentially (pK alpha = 6.3 for the CD site; pK alpha = 8.3 for EF site). The proteins also contrast with regard to their discrimination for Eu3+ over Ca2+. The CD and EF sites in rat parvalbumin both display a large preference for Eu3+: (KCa/KEu)CD = 143 +/- 11 and (KCa/KEu)EF = 191 +/- 30. However, in the case of oncomodulin, although the EF site of oncomodulin greatly prefers the trivalent lanthanide ion (KCa/KEu = 300 +/- 80), the CD site exhibits a relatively minor preference (KCa/KEu = 11 +/- 1).
Henzl
M T
MT
Department of Chemistry, New Mexico State University, Las Cruces 88003.
Birnbaum
E R
ER
D000818:Animals; D001665:Binding Sites; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D005063:Europium / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008114:Liver Neoplasms, Experimental / Q000378:metabolism; D009124:Muscle Proteins / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000378:metabolism*; D010320:Parvalbumins / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats; D011915:Rats, Inbred BUF; D012487:Salmonidae
D002135:Calcium-Binding Proteins; D009124:Muscle Proteins; D009363:Neoplasm Proteins; D010320:Parvalbumins; C034733:oncomodulin; D005063:Europium