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The Luminal N‐Terminus of Yeast Nvj1 is an Inner Nuclear Membrane Anchor
Author(s) -
Millen Jonathan I.,
Pierson Jason,
Kvam Erik,
Olsen Lars J.,
Goldfarb David S.
Publication year - 2008
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1111/j.1600-0854.2008.00789.x
Subject(s) - endoplasmic reticulum , biology , microbiology and biotechnology , inner membrane , saccharomyces cerevisiae , vacuole , translocase of the outer membrane , biogenesis , bacterial outer membrane , translocase of the inner membrane , membrane protein , membrane , protein targeting , biochemistry , mitochondrion , cytoplasm , inner mitochondrial membrane , yeast , mitochondrial membrane transport protein , escherichia coli , gene
The endoplasmic reticulum (ER) in Saccharomyces cerevisiae is largely divided between perinuclear and cortical compartments. Yeast Nvj1 localizes exclusively to small patches on the perinuclear ER where it interacts with Vac8 in the vacuole membrane to form nucleus–vacuole (NV) junctions. Three regions of Nvj1 mediate the biogenesis of NV junctions. A membrane‐spanning domain targets the protein to the ER. The C‐terminus binds Vac8 in the vacuole membrane, which induces the clustering of both proteins into NV junctions. The luminal N‐terminus is required for strict perinuclear localization. Three‐dimensional cryo‐electron tomography reveals that Nvj1 clamps the separation between the two nuclear membranes to half the width of bulk nuclear envelope. The N‐terminus contains a hydrophobic sequence bracketed by basic residues that resembles outer mitochondrial membrane signal‐anchors. The hydrophobic sequence can be scrambled or reversed without affecting function. Mutations that reduce the hydrophobicity of the core sequence or affect the distribution of basic residues cause mislocalization to the cortical ER. We conclude that the N‐terminus of Nvj1 is a retention sequence that bridges the perinuclear lumen and inserts into the inner nuclear membrane.