Mg2+ binding triggers rearrangement of the IM30 ring structure, resulting in augmented exposure of hydrophobic surfaces competent for membrane binding

The “inner membrane–associated protein of 30 kDa” (IM30), also known as “vesicle-inducing protein in plastids 1” (Vipp1), is found in the majority of photosynthetic organisms that use oxygen as an energy source, and its occurrence appears to be coupled to the existence of thylakoid membranes in cyan...

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Bibliographic Details
Published in:The Journal of biological chemistry 2018-05, Vol.293 (21), p.8230-8241
Main Authors: Heidrich, Jennifer, Junglas, Benedikt, Grytsyk, Natalia, Hellmann, Nadja, Rusitzka, Kristiane, Gebauer, Wolfgang, Markl, Jürgen, Hellwig, Petra, Schneider, Dirk
Format: Article
Language:English
Subjects:
circular dichroism
cyanobacteria
Fourier transform IR
IM30
isothermal titration calorimetry
membrane binding
membrane biogenesis
Membrane Biology
membrane biophysics
membrane fusion
Mg2
plant
protein denaturation
PspA
thylakoid membrane
Vipp1
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Summary:The “inner membrane–associated protein of 30 kDa” (IM30), also known as “vesicle-inducing protein in plastids 1” (Vipp1), is found in the majority of photosynthetic organisms that use oxygen as an energy source, and its occurrence appears to be coupled to the existence of thylakoid membranes in cyanobacteria and chloroplasts. IM30 is most likely involved in thylakoid membrane biogenesis and/or maintenance, and has recently been shown to function as a membrane fusion protein in presence of Mg2+. However, the precise role of Mg2+ in this process and its impact on the structure and function of IM30 remains unknown. Here, we show that Mg2+ binds directly to IM30 with a binding affinity of ∼1 mm. Mg2+ binding compacts the IM30 structure coupled with an increase in the thermodynamic stability of the proteins' secondary, tertiary, and quaternary structures. Furthermore, the structural alterations trigger IM30 double ring formation in vitro because of increased exposure of hydrophobic surface regions. However, in vivo Mg2+-triggered exposure of hydrophobic surface regions most likely modulates membrane binding and induces membrane fusion.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.RA117.000991