Old and new pathways of protein export in chloroplasts and bacteria.
Targeting of chloroplast proteins to the thylakoid membrane is analogous to bacterial secretion, and much of what we know has been learned from secretory mechanisms in Escherichia coli. However, chloroplasts also use a delta pH-dependent pathway to target thylakoid proteins, at least some of which are folded before transport. Previously, this pathway seemed to have no cognate in bacteria, but recent results have shown that the HCF106 gene in maize encodes a component of this pathway and has bacterial homologues. This delta pH-dependent pathway might be an ancient conserved mechanism for protein translocation that evolved before the endosymbiotic origin of plastids and mitochondria.
Settles
A M
AM
Cold Spring Harbor Laboratory, NY 11724, USA. martiens@cshl.org
Martienssen
R
R
D000595:Amino Acid Sequence; D029681:Arabidopsis Proteins; D001419:Bacteria / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism; D029968:Escherichia coli Proteins; D019204:GTP-Binding Proteins / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000378:metabolism; D010944:Plants / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D000069816:SEC Translocation Channels
D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C109236:Hcf106 protein, plant; D008565:Membrane Proteins; D010940:Plant Proteins; D011506:Proteins; D000069816:SEC Translocation Channels; C091479:SRP54A protein, Arabidopsis; C057841:SecY protein, E coli; D019204:GTP-Binding Proteins