The IM30/Vipp1 C-terminus associates with the lipid bilayer and modulates membrane fusion.
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.
Institut für Pharmazie und Biochemie, Johannes Gutenberg-Universität Mainz, 55128 Mainz, Germany.
Raoul
R
Hennig
Department of Biomedical Engineering, University of Minnesota, Twin Cities, MN, USA.
Ana
A
West
Institut für Pharmazie und Biochemie, Johannes Gutenberg-Universität Mainz, 55128 Mainz, Germany.
Martina
M
Debus
Institut für Zoologie, Johannes Gutenberg-Universität Mainz, 55128 Mainz, Germany.
Michael
M
Saur
Institut für Zoologie, Johannes Gutenberg-Universität Mainz, 55128 Mainz, Germany.
Jürgen
J
Markl
Department of Biomedical Engineering, University of Minnesota, Twin Cities, MN, USA.
Jonathan N
JN
Sachs
Institut für Pharmazie und Biochemie, Johannes Gutenberg-Universität Mainz, 55128 Mainz, Germany. Electronic address: Dirk.Schneider@uni-mainz.de.
Dirk
D
Schneider
D001426:Bacterial Proteins / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism; D008051:Lipid Bilayers / Q000378:metabolism*; D008561:Membrane Fusion / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism*; D008566:Membranes / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D000072417:Protein Domains; D046939:Synechocystis / Q000378:metabolism; D020524:Thylakoids / Q000378:metabolism*
D001426:Bacterial Proteins; D008051:Lipid Bilayers; D008565:Membrane Proteins
Membrane biogenesis; Membrane fusion; PspA; Thylakoid membrane; Vipp1