(A) Comparison of photoautotrophic growth phenotype under CCM-induced (air-level CO2) and CCM-repressed conditions (5% CO2, vol/vol). Abbreviations: WT, wild type; Spin, spinach hybrid; HAB, helix AB; HA, helix A; HB, helix B; Rcpr, reciprocal. (B) Western blot analysis of total soluble proteins. The 53-kDa LSU and 15- to 16-kDa SSU bands are marked. The variation in SSU size reflects the shorter form in spinach (123 amino acids, versus 140 in Chlamydomonas). Helix AB has a spinach-like SSU (except for the α-helices), whereas reciprocal has a Chlamydomonas-like SSU (except, again, for the α-helices). Histone H3 served as a loading control. Corresponding Coomassie-stained gel in shown in Fig. S2.