Transport of alpha-factor precursor from the endoplasmic reticulum to the Golgi apparatus has been reconstituted in gently lysed yeast spheroplasts. Transport is measured through the coupled addition of outer-chain carbohydrate to [35S]methionine-labeled alpha-factor precursor translocated into the endoplasmic reticulum of broken spheroplasts. The reaction is absolutely dependent on ATP, stimulated 6-fold by cytosol, and occurs between physically separable sealed compartments. Transport is inhibited by the guanine nucleotide analog GTP gamma S. sec23 mutant cells have a temperature-sensitive defect in endoplasmic reticulum-to-Golgi transport in vivo. This defect has been reproduced in vitro using sec23 membranes and cytosol. Transport at 30 degrees C with sec23 membranes requires addition of cytosol containing the SEC23 (wild-type) gene product. This demonstrates that an in vitro inter-organelle transport reaction depends on a factor required for transport in vivo. Complementation of sec mutations in vitro provides a functional assay for the purification of individual intercompartmental transport factors.

• PMID: 3293799
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Journal Article | Research Support, U.S. Gov't, Non-P.H.S. | Research Support, U.S. Gov't, P.H.S.

Authors

Baker D, Hicke L, Rexach M, Schleyer M, Schekman R

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