The cotranslational contacts between ribosome-bound nascent polypeptides and the subunits of the hetero-oligomeric chaperonin TRiC probed by photocross-linking.
The hetero-oligomeric eukaryotic chaperonin TRiC (TCP-1-ring complex, also called CCT) interacts cotranslationally with a diverse subset of newly synthesized proteins, including actin, tubulin, and luciferase, and facilitates their correct folding. A photocross-linking approach has been used to map the contacts between individual chaperonin subunits and ribosome-bound nascent chains of increasing length. Whereas a cryo-EM study suggests that chemically denatured actin interacts with only two TRiC subunits (delta and either beta or epsilon), actin and luciferase chains photocross-link to at least six TRiC subunits (alpha, beta, delta, epsilon, xi, and theta) at different stages of translation. Furthermore, the photocross-linking of actin, but not luciferase, nascent chains to TRiC subunits zeta and theta was length-dependent. In addition, a single photoreactive probe incorporated at a unique site in actin nascent chains of different lengths reacted covalently with multiple TRiC subunits, thereby indicating that the nascent chain samples the polypeptide binding sites of different subunits. We conclude that elongating actin and luciferase nascent chains contact multiple TRiC subunits upon emerging from the ribosome, and that the TRiC subunits contacted by nascent actin change as it elongates and starts to fold.
Etchells
Stephanie A
SA
Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, USA.
Meyer
Anne S
AS
Yam
Alice Y
AY
Roobol
Anne
A
Miao
Yiwei
Y
Shao
Yuanlong
Y
Carden
Martin J
MJ
Skach
William R
WR
Frydman
Judith
J
Johnson
Arthur E
AE
D000199:Actins / Q000737:chemistry; D000255:Adenosine Triphosphate / Q000737:chemistry; D001665:Binding Sites; D002460:Cell Line; D056404:Chaperonin Containing TCP-1; D018833:Chaperonins / Q000737:chemistry / Q000502:physiology*; D003432:Cross-Linking Reagents / Q000494:pharmacology; D020285:Cryoelectron Microscopy; D004591:Electrophoresis, Polyacrylamide Gel; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D008027:Light; D008156:Luciferases / Q000378:metabolism; D010455:Peptides / Q000737:chemistry*; D011485:Protein Binding; D014176:Protein Biosynthesis; D011506:Proteins / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D012343:RNA, Transfer / Q000378:metabolism; D012270:Ribosomes / Q000737:chemistry*
D000199:Actins; D003432:Cross-Linking Reagents; D010455:Peptides; D011506:Proteins; D012333:RNA, Messenger; D000255:Adenosine Triphosphate; D012343:RNA, Transfer; D008156:Luciferases; D056404:Chaperonin Containing TCP-1; D018833:Chaperonins