Extended Data Fig. 1: Biochemical and spectroscopic PBS characterization.

a, Representative protein composition analysis of the PBS sample by SDS-PAGE. Identification of the components by MS can be found in Supplementary Table 2. The purification was repeated at least three times, yielding the same results. b, Absorption, and fluorescence spectrum of the isolated PBS in 0.75 M K-phosphate pH 7.5. The PBS shows a maximum absorbance at 620 nm corresponding to phycocyanin (PC), and a shoulder at 650 nm corresponding to allophycocyanin (APC). The fluorescence peak maximum is ~670 nm when PC is preferentially excited (excitation at 580 nm), and a shoulder from 740 nm to 780 nm. c, Sucrose gradient of PBS showing the intense blue band that was used for cryo-EM. d, Fluorescence spectra of PBS before and after in vitro biotinylation. Collectively, these data show that the PBS preparation was structurally and functionally intact.