Molecular Bulkiness of a Single Amino Acid in the F1 α-Subunit Determines the Robustness of Cyanobacterial ATP Synthase

Cyanobacteria are promising photosynthetic organisms owing to their ease of genetic manipulation. Among them, Synechococcus elongatus UTEX 2973 exhibits faster growth, higher biomass production efficiency and more robust stress tolerance compared with S. elongatus PCC 7942. This is due to specific genetic differences, including four single-nucleotide polymorphisms (SNPs) in three genes. One of these SNPs alters an amino acid at position 252 of the F0F1 ATP synthase alpha-subunit from Tyr to Cys (alpha Y252C) in S. elongatus 7942. This change has been shown to significantly affect growth rate and stress tolerance, specifically in S. elongatus. Furthermore, experimental substitutions with several other amino acids have been shown to alter the ATP synthesis rate in the cell. In the present study, we introduced identical amino acid substitutions into Synechocystis sp. PCC 6803 at position 252 to elucidate the amino acid's significance and generality across cyanobacteria. We investigated the resulting impact on growth, intracellular enzyme complex levels, intracellular ATP levels and enzyme activity. The results showed that the alpha Y252C substitution decreased growth rate and high-light tolerance. This indicates that a specific bulkiness of this amino acid's side chain is important for maintaining cell growth. Additionally, a remarkable decrease in the membrane-bound enzyme complex level was observed. However, the alpha Y252C substitution did not affect enzyme activity or intracellular ATP levels. Although the mechanism of growth suppression remains unknown, the amino acid at position 252 is expected to play an important role in enzyme complex formation.

Automated summary

In this study, the importance of the amino acid at position 252 across cyanobacteria was elucidated by introducing amino acid substitutions in Synechocystis sp. PCC 6803. The results showed that the specific volume of this amino acid is crucial for maintaining cell growth and is related to enzyme complex formation.