High impact information on SFB3

• We show that the same site is conserved as a cargo-interaction domain on the Sec24p homolog Lst1p, which only packages a subset of the cargoes recognized by Sec24p [1].
• Furthermore, unlike Sec24p, Lst1p fails to bind to Bet1p in vitro, indicating a direct correlation between cargo binding and recruitment into vesicles [2].
• We show that Lst1p can function as a COPII subunit independently of Sec24p on native ER membranes and on synthetic liposomes [2].
• A tagged version of Lst1p was purified and eluted as a heterodimer complexed with Sec23p comparable to the Sec23/24p heterodimer [3].
• Furthermore, Pma1p coimmunoprecipitated with Lst1p and Sec24p from vesicles [3].

Anatomical context of SFB3

• Immunoelectronmicroscopic and biochemical studies revealed both Sec23/Lst1p and Sec23/24p on the membranes of the same vesicles [3].
• We found that cytosol from an lst1-null strain supported the packaging of alpha-factor precursor into COPII vesicles but was deficient in the packaging of Pma1p, the essential plasma membrane ATPase [3].
• Chromosomal deletion of LST1 is not lethal, but inhibits transport of the plasma membrane proton-ATPase (Pma1p) to the cell surface, causing poor growth on media of low pH [4].
• LST1 is a SEC24 homologue used for selective export of the plasma membrane ATPase from the endoplasmic reticulum [4].

Associations of SFB3 with chemical compounds

• Surprisingly, monomeric Pma1p present in ceramide-deficient membranes can be exported from the ER in COPII vesicles in a reaction that is stimulated by Lst1p [5].

Other interactions of SFB3

• Vesicles formed with a mixture of Sec23/Lst1p and Sec23/24p were similar morphologically and in their buoyant density, but larger than normal COPII vesicles (87-nm vs. 75-nm diameter) [3].
• We investigated the role of Lst1p, a Sec24p homologue, in cargo recruitment into COPII vesicles in Saccharomyces cerevisiae [3].
• Supplementation of mutant cytosol with purified Sec23/Lst1p restored Pma1p packaging into the vesicles [3].
• Sec24p and its two nonessential homologues Sfb2p and Sfb3p have been suggested to serve in cargo selection [6].

References