Vipp1: a very important protein in plastids?!

Vothknecht, Ute C.; Otters, Stephanie; Hennig, Raoul; Schneider, Dirk

doi:10.1093/jxb/err357

Cited by 94 publications

(140 citation statements)

References 101 publications

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“…25), these protein structures will trivially co-sediment with membranes. The closely related phage shock protein A (PspA) of Escherichia coli has been demonstrated to bind to the negatively charged lipid phosphatidylglycerol (PG) 26 , and thus IM30 binding to the negatively charged PG appears to be likely 27 . Mainly based on analyses of IM30-depleted chloroplasts and cyanobacteria, diverse functions have been suggested for IM30.…”

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confidence: 99%

“…Consequently, the name 'vesicle-inducing protein in plastids 1' (Vipp1) has been suggested. However, further studies have indicated that IM30 is involved in maintaining the structure and stability of internal membranes in chloroplasts and cyanobacteria, similar to its bacterial homologue PspA, and thus has a more protective function 27,28 . In addition, IM30 has been found to enhance protein translocation via the chloroplast Tat pathway 29 and involvement in photosystem biogenesis has been suggested 21,[30][31][32] .…”

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IM30 triggers membrane fusion in cyanobacteria and chloroplasts

et al. 2015

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The thylakoid membrane of chloroplasts and cyanobacteria is a unique internal membrane system harbouring the complexes of the photosynthetic electron transfer chain. Despite their apparent importance, little is known about the biogenesis and maintenance of thylakoid membranes. Although membrane fusion events are essential for the formation of thylakoid membranes, proteins involved in membrane fusion have yet to be identified in photosynthetic cells or organelles. Here we show that IM30, a conserved chloroplast and cyanobacterial protein of approximately 30 kDa binds as an oligomeric ring in a well-defined geometry specifically to membranes containing anionic lipids. Triggered by Mg 2 þ , membrane binding causes destabilization and eventually results in membrane fusion. We propose that IM30 establishes contacts between internal membrane sites and promotes fusion to enable regulated exchange of proteins and/or lipids in cyanobacteria and chloroplasts.

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IM30 triggers membrane fusion in cyanobacteria and chloroplasts

et al. 2015

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“…IM30 does not exhibit membrane spanning helices, as is typical for a canonical transmembrane protein (2, 3), and thus, it appears to peripherally bind to the cytoplasmic surface of the inner envelope/cytoplasmic membrane and TMs (5, 13). In fact, IM30 appears to exist in equilibrium between a soluble and a membrane-attached form (5).Based on computational analyses, IM30 contains seven ␣-helices, which are interrupted by small random coil domains, and these ␣-helices are predicted to be involved in the formation of coiled-coil structures (5,6,14,15). Although the tertiary structure of IM30 is not yet resolved, it is clear that IM30 monomers interact and assemble into large oligomeric ring complexes with molecular masses exceeding 2 MDa (5, 14).…”

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confidence: 99%

“…Based on computational analyses, IM30 contains seven ␣-helices, which are interrupted by small random coil domains, and these ␣-helices are predicted to be involved in the formation of coiled-coil structures (5,6,14,15). Although the tertiary structure of IM30 is not yet resolved, it is clear that IM30 monomers interact and assemble into large oligomeric ring complexes with molecular masses exceeding 2 MDa (5, 14).…”

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Organization into Higher Ordered Ring Structures Counteracts Membrane Binding of IM30, a Protein Associated with Inner Membranes in Chloroplasts and Cyanobacteria

Heidrich

Wulf

Hennig

et al. 2016

Journal of Biological Chemistry

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The IM30 (inner membrane-associated protein of 30 kDa), also known as the Vipp1 (vesicle-inducing protein in plastids 1), has a crucial role in thylakoid membrane biogenesis and maintenance. Recent results suggest that the protein binds peripherally to membranes containing negatively charged lipids. However, although IM30 monomers interact and assemble into large oligomeric ring complexes with different numbers of monomers, it is still an open question whether ring formation is crucial for membrane interaction. Here we show that binding of IM30 rings to negatively charged phosphatidylglycerol membrane surfaces results in a higher ordered membrane state, both in the head group and in the inner core region of the lipid bilayer. Furthermore, by using gold nanorods covered with phosphatidylglycerol layers and single particle spectroscopy, we show that not only IM30 rings but also lower oligomeric IM30 structures interact with membranes, although with higher affinity. Thus, ring formation is not crucial for, and even counteracts, membrane interaction of IM30.Engulfment of an ancient cyanobacterium by a primordial cell has resulted in the development of modern day chloroplasts, the organelles where photosynthesis takes place. Consequently, the fine structures of cyanobacterial cells and chloroplasts share many similarities. Notably, chloroplasts and cyanobacteria both contain an extra internal membrane system, the thylakoid membrane (TM) 2 network. Furthermore, both perform oxygenic photosynthesis, and the TMs harbor all protein complexes and pigments involved in the photosynthetic light reaction. However, although assembly and maintenance of TMs is vital for photosynthesis, the details of TM biogenesis and maintenance are still largely unsolved mysteries (1).In 1994 the IM30 (inner membrane-associated protein of 30 kDa) was discovered in chloroplasts of Pisum sativum (2), and a homologous protein appears to be expressed in almost every organism that is able to conduct oxygenic photosynthesis (2-5). Several in vivo studies have shown that the protein plays an essential role in TM formation and maintenance (reviewed in Ref. 6), e.g. the depletion of the protein in Arabidopsis thaliana or the cyanobacterium Synechocystis sp. PCC 6803 has resulted in a decreased amount of TMs (3, 7-9). Under cold stress conditions, depletion of IM30 resulted in the formation of vesicular structures at the chloroplast inner envelope membrane in Arabidopsis, which led to the name Vipp1 (vesicle inducing protein in plastids 1) (3). Nevertheless, although diverse physiological functions were proposed for IM30 in the past two decades, the exact protein function remained elusive for a long time. Only recently, IM30 has been identified to be able to reorganize lipid bilayer structures and to mediate membrane fusion in chloroplasts and cyanobacteria (10). Similar to its bacterial homolog, the PspA (phage shock protein A), which is involved in a bacterial stress response in situations provoking membrane stress (11), IM30 specifically interacts wi...

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Binding and/or hydrolysis of purine‐based nucleotides is not required for IM30 ring formation

et al. 2021

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IM30, the inner membrane-associated protein of 30 kDa, is conserved in cyanobacteria and chloroplasts. Although its exact physiological function is still mysterious, IM30 is clearly essential for thylakoid membrane biogenesis and/or dynamics. Recently, a cryptic IM30 GTPase activity has been reported, albeit thus far no physiological function has been attributed to this. Yet, it is still possible that GTP binding/hydrolysis affects formation of the prototypical large homo-oligomeric IM30 ring and rod structures. Here, we show that the Synechocystis sp. PCC 6803 IM30 protein in fact is an NTPase that hydrolyzes GTP and ATP, but not CTP or UTP, with about identical rates. While IM30 forms large oligomeric ring complexes, nucleotide binding and/or hydrolysis are clearly not required for ring formation.

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Vipp1: a very important protein in plastids?!

Cited by 94 publications

References 101 publications

IM30 triggers membrane fusion in cyanobacteria and chloroplasts

IM30 triggers membrane fusion in cyanobacteria and chloroplasts

Organization into Higher Ordered Ring Structures Counteracts Membrane Binding of IM30, a Protein Associated with Inner Membranes in Chloroplasts and Cyanobacteria

Binding and/or hydrolysis of purine‐based nucleotides is not required for IM30 ring formation

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