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Eu 3+ binding to europium‐regenerated bacteriorhodopsin upon delipidation and monomerization
Author(s) -
Heyes Colin D.,
Reynolds Keith B.,
El-Sayed Mostafa A.
Publication year - 2004
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/s0014-5793(04)00182-6
Subject(s) - europium , bacteriorhodopsin , chemistry , biochemistry , membrane , organic chemistry , ion
We have studied the effect of monomerization of the purple membrane lattice, as well as removal of 75% of the lipids, on the binding properties of Eu 3+ ions. We found that delipidation and monomerization do not cause the cations to lose their binding ability to the protein. This suggests that the three most strongly bound Eu 3+ cations do not bind to the lipids, but directly bind to the protein. Furthermore, we found that delipidation actually causes a slight increase in the binding affinity. This is likely a result of reduced aggregation of europium‐regenerated bacteriorhodopsin (bR) upon lipid removal causing more exposure of the binding sites to the Eu 3+ cations. These results, taken with those from our previous publication [Heyes and El‐Sayed, Biophys. J. 85 (2003) 426–434], might suggest that the cations remain bound upon delipidation of bR, but have no effect on the function. This is discussed with respect to the role of cations in the function of native bR.