Light Adaptation in Phycobilisome antennas: Influence on the Rod Length and Structural Arrangement

TL;DR

This study investigates how the length and structural arrangement of phycobilisome rods in cyanobacteria affect light absorption and excitation transfer efficiency, revealing an optimal rod length and proposing models for their structural organization.

Contribution

It introduces a model linking structural variations in phycobilisomes to their functional excitation transfer efficiency, supported by experimental structural data.

Findings

Optimal rod length maximizes average efficiency.

Efficiency of individual disks decreases with length.

Structural models predict transport properties across species.

Abstract

Phycobilisomes, the light-harvesting antennas of cyanobacteria, can adapt to a wide range of environments thanks to a composition and function response to stress conditions. We study how structural changes influence excitation transfer in these super-complexes. Specifically, we show the influence of the rod length on the photon absorption and subsequent excitation transport to the core. Despite the fact that the efficiency of individual disks on the rod decreases with increasing rod length, we find an optimal length for which the average rod efficiency is maximal. Combining this study with experimental structural measurements, we propose models for the arrangement of the phycobiliproteins inside the thylakoid membranes, evaluate the importance of rod length, and predict the corresponding transport properties for different cyanobacterial species. This analysis, which links the functional and structural properties of full phycobilisome complexes, thus provides further rationals to help resolving their exact structure.