Mathematical modeling of electron and proton transport coupled with ATP synthesis in chloroplasts

This study presents a mathematical model of electron and proton transport in higher plant chloroplasts built with allowance for lateral heterogeneity of their lamellar system. Numerical experiments were performed to examine how the lateral pH profiles in the inner thylakoid space and narrow gaps between adjacent granal thylakoids vary with the proton diffusion coefficient, pH in the stroma, and the metabolic conditions (photosynthetic control or photophosphorylation) in class B chloroplasts. The results of simulations suggest that regulation of electron and proton transport in chloroplasts in great measure relies on pH changes not only in the thylakoid lumen, but also in the gaps between adjacent granal thylakoids that may undergo alkalization because of the low rates of proton diffusion from the stroma to the photosystem II complexes localized in granal thylakoids.