GTP-binding Ypt1 protein and Ca2+ function independently in a cell-free protein transport reaction - PubMed (original) (raw)

GTP-binding Ypt1 protein and Ca2+ function independently in a cell-free protein transport reaction

D Baker et al. Proc Natl Acad Sci U S A. 1990 Jan.

Abstract

The 21-kDa GTP-binding Ypt1 protein (Ypt1p) is required for protein transport from the endoplasmic reticulum to the Golgi complex in yeast extracts. Ypt1 antibodies block transport; this inhibition is alleviated by competition with excess purified Ypt1p produced in bacteria. Furthermore, extracts of cells carrying the mutation ypt1-1 are defective in transport, but transport is restored if a cytosolic fraction from wild-type cells is provided. The in vitro transport reaction also requires physiological levels of Ca2+. However, Ypt1p functions independently of Ca2+. First, buffering the free Ca2+ at concentrations ranging from 1 nM to 10 microM does not relieve inhibition by Ypt1 antibodies. Second, consumption of a Ca2+-requiring intermediate that accumulates in Ca2+-deficient incubations is not inhibited by anti-Ypt1 antibodies, although completion of transport requires ATP and an N-ethylmaleimide-sensitive factor. Thus, Ypt1p and Ca2+ are required at distinct steps.

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References

    1. Cell. 1988 Jul 29;54(3):335-44 - PubMed
    1. J Biol Chem. 1951 Nov;193(1):265-75 - PubMed
    1. J Cell Biol. 1988 Sep;107(3):851-63 - PubMed
    1. Cell. 1988 Oct 21;55(2):309-20 - PubMed
    1. J Cell Biol. 1988 Oct;107(4):1465-76 - PubMed

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