The antenna complex functions as a light receptor, it captures and delivers excitation energy to photosystems I. The Prochlorales pcb genes are not related to higher plant LHCs. The antenna complex consists of divinyl chlorophylls (a and b) and divinyl chlorophyll a/b binding proteins and binds more divinyl chlorophyll b than does the antenna complex from high-light-adapted Prochlorococcus. Also forms complexes with PSI, consisting of a PSI trimer with surrounded by a PcbG ring (probably with 18 subunits). Is the only subunit found in this ring under iron-replete conditions. This transcript is moderately expressed at low and high light levels and is expressed somewhat more at 16 and 45 umol blue light/m2/s. The whole antenna complex is most highly expressed under low light; as the light levels increase antenna complex levels decrease. Thus at least in this strain the amount of antenna complex is controlled mostly at a post-transcriptional level. Transcription decreases upon iron starvation. This low-light-adapted strain contains 8 pcb genes. Belongs to the PsbB/PsbC family. IsiA/Pcb subfamily.