IM30/Vipp1 proteins are crucial for thylakoid membrane biogenesis in chloroplasts and cyanobacteria. A characteristic C-terminal extension distinguishes these proteins from the homologous bacterial PspA proteins, and this extension has been discussed to be key for the IM30/Vipp1 activity. Here we report that the extension of the Synechocystis IM30 protein is indispensable, and argue that both, the N-terminal PspA-domain as well as the C-terminal extension are needed in order for the IM30 protein to conduct its in vivo function. In vitro, we show that the PspA-domain of IM30 is vital for stability/folding and oligomer formation of IM30 as well as for IM30-triggered membrane fusion. In contrast, the IM30 C-terminal domain is involved in and necessary to stabilize defined contacts to negatively charged membrane surfaces, and to modulate the IM30-induced membrane fusion activity. Although the two IM30 protein domains have distinct functional roles, only together they enable IM30 to work properly.
Bibliographical noteFunding Information:
This work was funded by the Max-Planck graduate center at the Max Planck Institutes and the University of Mainz (to R.H and D.S.). A.W. and J.N.S. gratefully acknowledge funding from the National Institutes of Health ( R01 NS084998 to J.N.S.). All simulations were conducted using resources of Minnesota Supercomputing Institute ( https://www.msi.umn.edu /).
© 2016 Elsevier B.V.
- Membrane biogenesis
- Membrane fusion
- Thylakoid membrane