The high-concentration CO2-requiring mutant N5 of Synechococcus sp. PCC 7942 was obtained by the insertion of a kanamycin-resistant gene at the EcoRI site, 12.4 kb upstream of rbc. The mutant is unable to accumulate inorganic carbon internally and exhibits very low apparent photosynthetic affinity for inorganic carbon but a photosynthetic Vmax similar to that of the wild type. Sequence and nort...