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Role of the proline knot motif in oleosin endoplasmic reticulum topology and oil body targeting.
Plant Cell. 1997 Aug; 9(8):1481-93.PC

Abstract

An Arabidopsis oleosin was used as a model to study oleosin topology and targeting to oil bodies. Oleosin mRNA was in vitro translated with canine microsomes in a range of truncated forms. This allowed proteinase K mapping of the membrane topology. Oleosin maintains a conformation with a membrane-integrated hydrophobic domain flanked by N- and C-terminal domains located on the outer microsome surface. This is a unique membrane topology on the endoplasmic reticulum (ER). Three universally conserved proline residues within the "proline knot" motif of the oleosin hydrophobic domain were substituted by leucine residues. After in vitro translation, only minor differences in proteinase K protection could be observed. These differences were not apparent in soybean microsomes. No significant difference in incorporation efficiency on the ER was observed between the two oleosin forms. However, as an oleosin-beta-glucuronidase translational fusion, the proline knot variant failed to target to oil bodies in both transient embryo expression and in stably transformed seeds. Fractionation of transgenic embryos expressing oleosin-beta-glucuronidase fusions showed that the proline knot variant accumulated in the ER to similar levels compared with the native form. Therefore, the proline knot motif is not important for ER integration and the determination of topology but is required for oil body targeting. The loss of the proline knot results in an intrinsic instability in the oleosin polypeptide during trafficking.

Authors+Show Affiliations

Department of Biological Sciences, University of Calgary, Alberta, Canada.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

9286116

Citation

Abell, B M., et al. "Role of the Proline Knot Motif in Oleosin Endoplasmic Reticulum Topology and Oil Body Targeting." The Plant Cell, vol. 9, no. 8, 1997, pp. 1481-93.
Abell BM, Holbrook LA, Abenes M, et al. Role of the proline knot motif in oleosin endoplasmic reticulum topology and oil body targeting. Plant Cell. 1997;9(8):1481-93.
Abell, B. M., Holbrook, L. A., Abenes, M., Murphy, D. J., Hills, M. J., & Moloney, M. M. (1997). Role of the proline knot motif in oleosin endoplasmic reticulum topology and oil body targeting. The Plant Cell, 9(8), 1481-93.
Abell BM, et al. Role of the Proline Knot Motif in Oleosin Endoplasmic Reticulum Topology and Oil Body Targeting. Plant Cell. 1997;9(8):1481-93. PubMed PMID: 9286116.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Role of the proline knot motif in oleosin endoplasmic reticulum topology and oil body targeting. AU - Abell,B M, AU - Holbrook,L A, AU - Abenes,M, AU - Murphy,D J, AU - Hills,M J, AU - Moloney,M M, PY - 1997/8/1/pubmed PY - 1997/8/1/medline PY - 1997/8/1/entrez SP - 1481 EP - 93 JF - The Plant cell JO - Plant Cell VL - 9 IS - 8 N2 - An Arabidopsis oleosin was used as a model to study oleosin topology and targeting to oil bodies. Oleosin mRNA was in vitro translated with canine microsomes in a range of truncated forms. This allowed proteinase K mapping of the membrane topology. Oleosin maintains a conformation with a membrane-integrated hydrophobic domain flanked by N- and C-terminal domains located on the outer microsome surface. This is a unique membrane topology on the endoplasmic reticulum (ER). Three universally conserved proline residues within the "proline knot" motif of the oleosin hydrophobic domain were substituted by leucine residues. After in vitro translation, only minor differences in proteinase K protection could be observed. These differences were not apparent in soybean microsomes. No significant difference in incorporation efficiency on the ER was observed between the two oleosin forms. However, as an oleosin-beta-glucuronidase translational fusion, the proline knot variant failed to target to oil bodies in both transient embryo expression and in stably transformed seeds. Fractionation of transgenic embryos expressing oleosin-beta-glucuronidase fusions showed that the proline knot variant accumulated in the ER to similar levels compared with the native form. Therefore, the proline knot motif is not important for ER integration and the determination of topology but is required for oil body targeting. The loss of the proline knot results in an intrinsic instability in the oleosin polypeptide during trafficking. SN - 1040-4651 UR - https://www.unboundmedicine.com/medline/citation/9286116/Role_of_the_proline_knot_motif_in_oleosin_endoplasmic_reticulum_topology_and_oil_body_targeting_ L2 - http://www.plantcell.org/cgi/pmidlookup?view=long&pmid=9286116 DB - PRIME DP - Unbound Medicine ER -