Publication Date:
2016-06-25
Description:
The binding properties of Ca 2+ to EF-hand I of aequorin (AQ) were characterized by replacing the loop sequence of EF-hand I (AQ[I]) with other known loop sequences of Ca 2+ -binding proteins, including photoproteins (aequorin, clytin-I, clytin-II and mitrocomin), Renilla luciferin-binding protein (RLBP) and calmodulin (CaM). For evaluation of the binding affinity of Ca 2+ to AQ[I] mutants, the half-decay time of the maximum intensity in the luminescence reaction triggered by Ca 2+ was used as an indicator and 22 kinds of AQ[I] mutants were expressed in Escherichia coli cells. AQ[I] mutants replaced with the EF-hand I and EF-hand III from photoproteins showed sufficient luminescence activity, but it was not shown by other EF-hands from RLBP and CaM. An AQ[I] mutant with a lysine or arginine residue at the second position of the non-conserved amino acid residue showed a slow-decay pattern of luminescence, indicating that the Ca 2+ -binding affinity to aequorin was reduced by a positive charge at the second position of the loop sequence. The specific loop sequence of the EF-hand I motif in aequorin caused the specific Ca 2+ -triggered luminescence pattern.
Print ISSN:
0021-924X
Electronic ISSN:
1756-2651
Topics:
Biology
,
Chemistry and Pharmacology
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