DnaK3 Is Involved in Biogenesis and/or Maintenance of Thylakoid Membrane Protein Complexes in the Cyanobacterium Synechocystis sp. PCC 6803.

Adrien Thurotte,Ruven Jilly,Dirk Schneider,Tobias Seidel,Uwe Kahmann

doi:10.3390/life10050055

Abstract

DnaK3, a highly conserved cyanobacterial chaperone of the Hsp70 family, binds to cyanobacterial thylakoid membranes, and an involvement of DnaK3 in the biogenesis of thylakoid membranes has been suggested. As shown here, light triggers synthesis of DnaK3 in the cyanobacterium Synechocystis sp. PCC 6803, which links DnaK3 to the biogenesis of thylakoid membranes and to photosynthetic processes. In a DnaK3 depleted strain, the photosystem content is reduced and the photosystem II activity is impaired, whereas photosystem I is regular active. An impact of DnaK3 on the activity of other thylakoid membrane complexes involved in electron transfer is indicated. In conclusion, DnaK3 is a versatile chaperone required for biogenesis and/or maintenance of thylakoid membrane-localized protein complexes involved in electron transfer reactions. As mentioned above, Hsp70 proteins are involved in photoprotection and repair of PS II in chloroplasts.

Highlights

In plants and cyanobacteria, the biogenesis and dynamics of thylakoid membranes (TMs) is light-controlled [1,2]
While dark-adapted Synechocystis cells do not harbor active photosystem II (PS II) complexes, complete photosynthetic activity is regained within 24 h after transferring dark-adapted cells into the light, and reappearance of photosynthetic electron transfer processes is coupled to the formation of internal TMs [7]
Three different DnaK proteins are expressed in the cyanobacterium Synechocystis sp

Summary

Introduction

The biogenesis and dynamics of thylakoid membranes (TMs) is light-controlled [1,2]. While dark-adapted Synechocystis cells do not harbor active photosystem II (PS II) complexes, complete photosynthetic activity is regained within 24 h after transferring dark-adapted cells into the light, and reappearance of photosynthetic electron transfer processes is coupled to the formation of internal TMs [7]. It is still enigmatic how the formation of internal TMs is controlled, both in chloroplasts and cyanobacteria, some proteins that might be involved in this process have already been described previously [8]. These proteins include the inner membrane-associated protein of 30 kDa (IM30, known as Vipp: The vesicle-inducing protein in plastids 1), Hsp (Heat shock protein 70) chaperones, dynamin-like proteins, a prohibitin-like protein, Life 2020, 10, 55; doi:10.3390/life10050055 www.mdpi.com/journal/life

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