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The ER junction-forming protein, Lunapark, LNP1 of 278 aas and possibly 2 N-terminal TMSs or 4 TMSs in a 2 + 2 arrangement with two N-terminal and 2 more C-terminal (Chen et al. 2012).  LNP1 aids in membrane fusion and maintenance of the endoplasmic reticulum (Casey et al. 2015). Works in conjunction with the ER shaping proteins (reticulons RTN1 and RTN2 (TC# 8.A.102), YOP1), and in antagonism to SEY1 to maintain the network in a dynamic equilibrium. May counterbalance SEY1-directed polygon formation by promoting polygon loss through ring closure (Chen et al. 2012).

LNP1 of Saccharomyces cerevisiae

Lunapark LNP1 of 408 aas and 2 N-terminal TMSs. Kriechbaumer et al. 2018 identified two Arabidopsis LNP homologues and investigated their subcellular localization via confocal microscopy and potential function in shaping the ER network using protein-protein interaction assays and mutant analysis. They showed that AtLNP1 overexpression in tobacco leaf epidermal cells mainly labels cisternae in the ER network, whereas AtLNP2 labels the whole ER. Overexpression of LNP proteins resulted in an increased abundance of ER cisternae. AtLNP1 and AtLNP2 appear to be involved in determining the network morphology of the plant ER, possibly by regulating the formation of ER cisternae (Kriechbaumer et al. 2018).

LNP1 of Arabidopsis thaliana

At LNP2 of 409 aas and 2 N-terminal TMSs (Kriechbaumer et al. 2018).