Department of Biochemistry
Protein targeting and folding in plants AREAS: Oorganelle biogenesis, posttranslational modifications.
Plant cells contain many complex membrane-limited subcellular compartments whose proteins are synthesized primarily within the cytoplasm. A key question is how proteins get from the cytoplasm to their final location within the organelle. Further, how are proteins maintained in unfolded form during transit from the cytoplasm and then correctly folded and assembled within the organelle? It is known that a class of proteins, termed chaperones, assist this targeting, folding, and assembly.
One class of chaperones consists of proteins related to the 70,000 molecular weight heat-shock or stress-related proteins (Stress70s). Specific forms of Stress70 are located within all compartments. In the cytoplasm, Stress70 binds to the nascent polypeptide emerging from the ribosome and maintains it in an unfolded conformation. ATP is required and rates of ATP hydrolysis are regulated by covalent modification of the chaperones and by association with accessory co-chaperones. Conversely, organellar Stress70 assists in correctly folding a polypeptide once it is transported into the organelle interior. Current research focuses on the nature of the interactions between newly synthesized polypeptides, the Stress70 molecular chaperones, and the ATPase-regulating co-chaperones.
Localization of the atDjC6 and atDjC37 co-chaperone proteins by scanning laser confocal microscopy. Tobacco BY-2 cells were transformed by particle bombardment to to express atDjC6-GFP (B) and atDjC37-RFP (C). Where the green and red fluorescent images are coincident, the merged images appear as yellow (C). Panel A is a differential interference microscopy (Nomarski) image of the same cell.