LHCA4 residues surrounding red chlorophylls allow for fine-tuning of the spectral region for photosynthesis in .

Improving far-red light utilization could be an approach to increasing crop production under suboptimal conditions. In land plants, only a small part of far-red light can be used for photosynthesis, which is captured by the antenna proteins LHCAs of photosystem I (PSI) through the chlorophyll (Chl) pair 603 and 609. However, it is unknown how the energy level of Chls 603-609 is fine-tuned by the local protein environment .

Assembly of LHCA5 into PSI blue shifts the far-red fluorescence emission in higher plants.

In higher plants, the PSI core complex is associated with light-harvesting complex I (LHCI), forming the PSI-LHCI super-complex. In vascular plants, four major antenna proteins (LHCA1-4) are assembled in the order of LHCA1, LHCA4, LHCA2, and LHCA3 into a crescent-shaped LHCI, while LHCA5 and LHCA6 are minor antenna proteins. By contrast, in moss and green algae, LHCA5 or LHCA5-like protein functions as one of the major antenna proteins by residing at the second site of LHCI.