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Title: GTP promotes the formation of early-import intermediates but is not required during the translocation step of protein import into chloroplasts

Abstract

Protein import into chloroplasts is an energy-requiring process mediated by a pertinacious import apparatus. Although previous work has shown that low levels of ATP or GTP can support precursor binding, the role of GTP during the import process remains unclear. Specifically, it is unknown whether GTP plays a separate role from ATP during the early stages of protein import and whether GTP has any role in the later stages of transport. The authors investigated the role of GTP during the various stages of protein import into chloroplasts by using purified GTP analogs and an in vitro import assay. GTP, GDP, the nonhydrolyzable analog GMP-PNP, and the slowly hydrolyzable analogs guanosine 5{prime}-O-(2-thiodiphosphate) and guanosine 5{prime}-O-(3-thiotriphosphate) were used in this study. Chromatographically purified 5{prime}-guanylyl-imido-diphosphate and guanosine 5{prime}-O-(3-thiotriphosphate) were found to inhibit the formation of early-import intermediates, even in the presence of ATP. The authors also observed that GTP does not play a role during the translocation of precursors from the intermediate state. They conclude that GTP hydrolysis influences events leading to the formation of early-import intermediates, but not subsequent steps such as precursor translocation.

Authors:
; ;
Publication Date:
Research Org.:
Michigan State Univ., East Lansing, MI (US)
Sponsoring Org.:
National Science Foundation; US Department of Energy
OSTI Identifier:
20006207
Alternate Identifier(s):
OSTI ID: 20006207
Resource Type:
Journal Article
Journal Name:
Plant Physiology (Bethesda)
Additional Journal Information:
Journal Volume: 121; Journal Issue: 1; Other Information: PBD: Sep 1999; Journal ID: ISSN 0032-0889
Country of Publication:
United States
Language:
English
Subject:
55 BIOLOGY AND MEDICINE, BASIC STUDIES; CHLOROPLASTS; MEMBRANE PROTEINS; ATP; GUANYLIC ACID; TRANSLOCATION; BIOLOGICAL PATHWAYS; MEMBRANE TRANSPORT

Citation Formats

Young, M.E., Keegstra, K., and Froehlich, J.E. GTP promotes the formation of early-import intermediates but is not required during the translocation step of protein import into chloroplasts. United States: N. p., 1999. Web. doi:10.1104/pp.121.1.237.
Young, M.E., Keegstra, K., & Froehlich, J.E. GTP promotes the formation of early-import intermediates but is not required during the translocation step of protein import into chloroplasts. United States. doi:10.1104/pp.121.1.237.
Young, M.E., Keegstra, K., and Froehlich, J.E. Wed . "GTP promotes the formation of early-import intermediates but is not required during the translocation step of protein import into chloroplasts". United States. doi:10.1104/pp.121.1.237.
@article{osti_20006207,
title = {GTP promotes the formation of early-import intermediates but is not required during the translocation step of protein import into chloroplasts},
author = {Young, M.E. and Keegstra, K. and Froehlich, J.E.},
abstractNote = {Protein import into chloroplasts is an energy-requiring process mediated by a pertinacious import apparatus. Although previous work has shown that low levels of ATP or GTP can support precursor binding, the role of GTP during the import process remains unclear. Specifically, it is unknown whether GTP plays a separate role from ATP during the early stages of protein import and whether GTP has any role in the later stages of transport. The authors investigated the role of GTP during the various stages of protein import into chloroplasts by using purified GTP analogs and an in vitro import assay. GTP, GDP, the nonhydrolyzable analog GMP-PNP, and the slowly hydrolyzable analogs guanosine 5{prime}-O-(2-thiodiphosphate) and guanosine 5{prime}-O-(3-thiotriphosphate) were used in this study. Chromatographically purified 5{prime}-guanylyl-imido-diphosphate and guanosine 5{prime}-O-(3-thiotriphosphate) were found to inhibit the formation of early-import intermediates, even in the presence of ATP. The authors also observed that GTP does not play a role during the translocation of precursors from the intermediate state. They conclude that GTP hydrolysis influences events leading to the formation of early-import intermediates, but not subsequent steps such as precursor translocation.},
doi = {10.1104/pp.121.1.237},
journal = {Plant Physiology (Bethesda)},
issn = {0032-0889},
number = 1,
volume = 121,
place = {United States},
year = {1999},
month = {9}
}