Photosynthetic electron transfer occurs efficiently in specialized internal membranes known as thylakoid membranes. Thylakoid membranes exhibit diverse structural variations across photoautotrophic organisms. We studied how a key protein, CurT, shapes thylakoid membranes of a model cyanobacterium Synechococcus elongatus PCC 7942 (Syn7942), a rod-shaped cyanobacterium with regular concentric thylakoid layers. By guiding the curves and structure of thylakoid membranes, CurT helps the cells capture light efficiently, especially when conditions change. The detailed characterization of the role of CurT in Syn7942 offers new clues about how nature builds high-performance photosynthetic membrane systems in response to environmental fluctuations. These findings may inspire future ways to redesign photosynthetic membranes for better crop yields or cleaner bioenergy production.