title: The mechanism of inactivation of a 50-pS envelope anion channel during chloroplast protein import.
abstract: The mechanism of import-competent precursor protein-induced inactivation of a 50-pS anion channel of the chloroplast envelope is investigated using single-channel recordings. The inactivation by precursor protein is the result of the induction of a long-lived closed state of the channel. The mean duration of this state does not depend on precursor concentration. From this it can be concluded that the protein import related anion channel enters the inactive state less frequently when the precursor concentration is lowered, but that the time spent in this state remains the same. Furthermore, it was found that the presence of precursor protein also decreases the mean durations of preexisting open and closed states of the channel. This decrease is found to be dependent on the precursor concentration. From this it is concluded that there is a direct interaction between the precursor protein and a protein complex of which the channel is a constituent. The mean duration of the precursor-induced long-lived closed state does not depend on the length of the translocation-competent precursor. This suggests that the duration of import is independent of precursor length.
authors.affiliation: Laboratory of Plant Physiology, Wageningen Agricultural University, 6703 BD Wageningen, The Netherlands. paul.vandenwijngaard@guest.pf.wau.nl
authors.forename: P W
authors.initials: PW
authors.lastname: van den Wijngaard
authors.forename: C
authors.initials: C
authors.lastname: Dabney-Smith
authors.forename: B D
authors.initials: BD
authors.lastname: Bruce
authors.forename: W J
authors.initials: WJ
authors.lastname: Vredenberg
mesh_terms: D001693:Biological Transport, Active; D055592:Biophysical Phenomena; D001703:Biophysics; D002736:Chloroplasts / Q000378:metabolism*; D005288:Ferredoxins / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism; D007473:Ion Channels / Q000037:antagonists & inhibitors* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010940:Plant Proteins / Q000378:metabolism*; D011498:Protein Precursors / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism
chemical_list: D005288:Ferredoxins; D007473:Ion Channels; D010940:Plant Proteins; D011498:Protein Precursors; D011994:Recombinant Proteins; D012273:Ribulose-Bisphosphate Carboxylase