A TCP1-related molecular chaperone from plants refolds phytochrome to its photoreversible form.
Folding of the major cytoskeletal components in the cytosol of mammalian cells is mediated by interactions with t-complex polypeptide-1 (TCP1) molecular chaperones, a situation analogous to the chaperonin 60-aided folding of polypeptides in bacteria, chloroplasts and mitochondria. We have purified a TCP1-related molecular chaperone from etiolated oat seedlings that has a unique structure. Although immunologically related to TCP1, and having amino-acid sequence similarity, its quaternary structure is different from animal TCP1 proteins. Electron microscopy and image analysis reveals that the chaperone has two stacked rings of six subunits each, and is distinct in size and configuration. The chaperone copurifies with the soluble cytosolic photoreceptor phytochrome, and can stimulate refolding of denatured phytochrome to a photoactive form in the presence of Mg-ATP. We propose that this protein is the cytosolic chaperone involved in phytochrome biogenesis in plant cells.
Mummert
E
E
Institut für Biologie 2, Freiburg, Germany.
Grimm
R
R
Speth
V
V
Eckerskorn
C
C
Schiltz
E
E
Gatenby
A A
AA
Schäfer
E
E
D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D018833:Chaperonins; D003429:Cross Reactions; D002523:Edible Grain / Q000737:chemistry*; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D008869:Microtubule-Associated Proteins; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000276:immunology; D010834:Phytochrome / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry / Q000302:isolation & purification* / Q000648:ultrastructure; D017510:Protein Folding; D011506:Proteins / Q000737:chemistry / Q000302:isolation & purification* / Q000502:physiology / Q000648:ultrastructure; D017386:Sequence Homology, Amino Acid; D044767:Ubiquitin-Protein Ligases; D056427:t-Complex Genome Region
D047908:Intracellular Signaling Peptides and Proteins; D008869:Microtubule-Associated Proteins; D009687:Nuclear Proteins; D010940:Plant Proteins; D011506:Proteins; D010834:Phytochrome; D000255:Adenosine Triphosphate; C116196:PPP1R11 protein, human; D044767:Ubiquitin-Protein Ligases; D018833:Chaperonins