Abstract
Tail-anchored (TA) proteins insert post-translationally into the membrane of the endoplasmic reticulum (ER) and span the membrane by their C-terminal transmembrane domain. We have reconstituted membrane insertion of TA proteins from recombinant Asna1/TA protein complexes and ER-derived membranes. Our data show that Asna1 can mediate membrane insertion of RAMP4 and Sec61beta without the participation of other cytosolic proteins by a mechanism that depends on the presence of ATP or ADP and a protease-sensitive receptor in the ER membrane. By contrast, membrane insertion of cytochrome b5 can proceed independently of Asna1 and nucleotides.
Highlights
Tail-anchored (TA) proteins belong to a special class of membrane proteins that insert post-translationally into the membrane of the endoplasmic reticulum (ER) and into the mitochondrial outer membrane (Borgese et al, 2003a)
Our data show that Asna1 can mediate membrane insertion of ribosomeassociated membrane protein 4 (RAMP4) and Sec61 without the participation of other cytosolic proteins by a mechanism that depends on the presence of ATP or ADP and a proteasesensitive receptor in the ER membrane
Purification of a soluble Asna1/TA protein complex and membrane insertion of the TA protein It has previously been shown that the mammalian ATPase Asna1 associates with the newly synthesized TA proteins RAMP4op and Sec61 op before they are inserted into membranes derived from the rough ER, rough microsomes (RMs) (Favaloro et al, 2008; Stefanovic and Hegde, 2007)
Summary
Tail-anchored (TA) proteins belong to a special class of membrane proteins that insert post-translationally into the membrane of the endoplasmic reticulum (ER) and into the mitochondrial outer membrane (Borgese et al, 2003a). The C-terminal location of this signal poses a unique challenge to membrane targeting of the completed protein, as hydrophobic TMDs are prone to aggregation. To cope with this problem, cells have evolved diverse mechanisms for chaperoning the newly synthesized membrane protein and targeting it to its destination membrane (Borgese et al, 2007; Rabu et al, 2009)
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