Consider an Engineered Chimeric Protein Made from Fusion of Three

Consider an engineered chimeric protein made from fusion of three proteins: a blue fluorescent protein (BFP) , a calmodulin-binding peptide, and a green fluorescent protein (GFP) . Calmodulin is an abundant calcium-binding protein in eukaryotes. Once bound to calcium ions, it can recognize the calmodulin-binding peptide in the fusion protein, change conformation, wrap around the peptide, and bring the BFP and GFP components in close proximity. This results in fluorescence resonance energy transfer (FRET) between BFP and GFP. Accordingly, the fusion protein …

A) is a luminescent ion-sensitive indicator that red-shifts its emission wavelength in the presence of calcium.
B) is a luminescent ion-sensitive indicator that increases its emission in the presence of calcium.
C) is a genetically encoded calcium indicator that red-shifts its emission wavelength in the presence of calcium.
D) is a genetically encoded calcium indicator that increases its emission in the presence of calcium.