Mutational and Biochemical Analysis of Plasma Membrane Targeting Mediated by the Farnesylated, Polybasic Carboxy Terminus of K-ras4B
Mutational analysis and in vitro assays of membrane association have been combined to investigate the mechanism of plasma membrane targeting mediated by the farnesylated, polybasic carboxy-terminal sequence of K-ras4B in mammalian cells. Fluorescence-microscopic localization of chimeric proteins lin...
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Published in | Biochemistry (Easton) Vol. 39; no. 28; pp. 8298 - 8307 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
United States
American Chemical Society
18.07.2000
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Subjects | |
Online Access | Get full text |
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Summary: | Mutational analysis and in vitro assays of membrane association have been combined to investigate the mechanism of plasma membrane targeting mediated by the farnesylated, polybasic carboxy-terminal sequence of K-ras4B in mammalian cells. Fluorescence-microscopic localization of chimeric proteins linking the enhanced green fluorescent protein (EGFP) to the K-ras4B carboxy-terminal sequence, or to variant forms of this sequence, reveals that the normal structure of this targeting motif can be greatly altered without compromising plasma membrane-targeting activity so long as an overall strongly polybasic/amphiphilic character is retained. An EGFP/K-ras4B(171−188) chimeric protein was readily abstracted from isolated cell membranes by negatively charged lipid vesicles, and this abstraction was markedly enhanced by the anionic lipid-binding agent neomycin. Our results strongly favor a mechanism in which at the plasma membrane the carboxy-terminal sequence of K-ras4B associates not with a classical specific proteinaceous receptor but rather with nonspecific but highly anionic ‘sites' formed at least in part by the membrane lipid bilayer. Our findings also suggest that the recently demonstrated prenylation-dependent trafficking of immature forms of K-ras4B through the endoplasmic reticulum [Choy et al. (1999) Cell 98, 69−80], while required for maturation of the protein, beyond this stage may not be essential to allow the ultimate delivery of the mature protein to the plasma membrane. |
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Bibliography: | This work was supported by an operating grant from the Medical Research Council of Canada (Grant MT-7776) to J.R.S. and by a postdoctoral fellowship award to M.-O.R. from la Fondation pour la Recherche Médicale (Paris). istex:0F11C0ECAAF92CA89DB2E0CF617F064459B69571 ark:/67375/TPS-GC01W9GT-J ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0006-2960 1520-4995 |
DOI: | 10.1021/bi000512q |