Osaka Bioscience Institute, Japan.
The requirement for a proline residue at the C-terminus of the Ca(2+)-binding photoprotein, aequorin, was investigated by measuring luminescence activities of a series of C-terminal deletion mutants, substitution mutants and an addition mutant. CD spectral measurements of apoaequorin with the C-terminal proline deleted showed a small change in secondary structure. In all cases studied, the C-terminal proline was required for bioluminescence activity.