Table 1.

Absorption spectral parameters for TCCP sensors with different bilin chromophores

Recombinant photosensory core domain (PAS-GAF-PHY) constructs were purified after expression in E. coli cultures synthesizing BV, PCB, or PΦB (from Fig. 3 and Fig. S2) and desalted and concentrated in 50 mm Tris-HCl buffer, pH 8.

Protein	Bilin	λmaxa 15Z; 15E	SARb	Ycc	%ΔAd
ToTCCP	BV	411; 424	0.22*	NAe	47.5 (0.287)
	PCB	414; 662	0.32	0.611	100 (0.604)
	PΦB	435; 615	0.25	0.502	91.4 (0.552)
ScTCCP	BV	401; 401	0.26*	NA	27.1 (0.181)
	PCB	401; 571	0.23	0.385	100 (0.667)
	PΦB	414; 594	0.10	0.176	45.9 (0.306)
GlTCCP	BV	426; 607	0.07*	NA	28.2 (0.072)
	PCB	408; 581	0.10	0.117	100 (0.256)
	PΦB	429; 598	0.02	0.024	44.5 (0.114)
NpTCCP	PCB	392; 598,670	0.22	NA	85.0

^a Peak wavelengths are reported for the bilin transition of longest wavelength (S¹) as 15Z or 15E. Multiple values for the 15E state of NpTCCP reflect thermal evolution of the yellow-orange intermediate to a red-absorbing photoproduct (15).

^b Specific absorbance ratio (SAR) values of acid-urea denatured proteins were calculated as the ratio of the peak absorbance of the bilin band and the protein band at 280 nm, serving as a relative measure of chromophore-binding efficiency. For BV adducts, SAR values indicated with asterisks correspond to native proteins due to instability of the presumed non-covalent adducts under acid denaturing conditions

^c Chromophorylation yield (Y_c) was calculated as the ratio of bound chromophore to protein content (see “Experimental procedures” for details).

^d Relative photoconversion efficiency of native BV- or PΦB- chromophorylated proteins (%ΔΔA) to respective PCB-chromophorylated proteins were provided. Photoconversion efficiency given in parentheses was determined by subtracting the 15E spectrum from the 15Z spectrum. Spectra were normalized to the blue band absorbance prior to the calculation. Values in parentheses are photoconversion efficiency.

^e NA, not applicable.