Identification of two GTP-binding proteins in the chloroplast protein import machinery

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Science  11 Nov 1994:
Vol. 266, Issue 5187, pp. 1035-1039
DOI: 10.1126/science.7973656


Two of four proteins that associated with translocation intermediates during protein import across the outer chloroplast envelope membrane were identified as guanosine triphosphate (GTP)-binding proteins. Both proteins are integral membrane proteins of the outer chloroplast membrane, and both are partially exposed on the chloroplast surface where they were accessible to thermolysin digestion. Engagement of the outer membrane's import machinery by an import substrate was inhibited by slowly hydrolyzable or non-hydrolyzable GTP analogs. Thus, these GTP-binding proteins may function in protein import into chloroplasts.

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