Protein sorting to the vacuolar membrane.
AUTOR(ES)
Höfte, H
RESUMO
The vacuolar membrane (tonoplast) of plant cells contains a polytopic integral membrane protein with six membrane-spanning domains and cytoplasmically oriented amino-terminal and carboxy-terminal domains. This protein, tonoplast intrinsic protein (TIP), is a member of the membrane intrinsic protein (MIP) family of proteins, a family of channel proteins found in a variety of organisms. In bean seeds, alpha-TIP is synthesized on the rough endoplasmic reticulum and its transport to the tonoplast is mediated by the secretory system. In this study, we report that a polypeptide segment that includes the sixth membrane domain and the cytoplasmic tail of 18 amino acids of alpha-TIP is sufficient to target the reporter protein phosphinotricine acetyltransferase to the tonoplast of stably transformed tobacco cells. To determine if the carboxy-terminal cytoplasmic tail of alpha-TIP contains important tonoplast targeting information, a deletion construct lacking the 15 carboxy-terminal amino acids was introduced for transient expression in tobacco cells; we found that the slightly truncated protein still accumulated in the tonoplast. From these results, we concluded that a transmembrane domain of a tonoplast protein probably contains sufficient information for transport to the tonoplast. Whether such transport occurs by bulk flow or involves specific cellular machinery remains to be determined.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=160191Documentos Relacionados
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