TY - JOUR
T1 - Encapsulation of an 86-kDa assembly intermediate inside the cavities of GroEL and its single-ring variant SR1 by GRoES
AU - Song, Jiu Li
AU - Li, Jun
AU - Huang, Yi Shuian
AU - Chuang, David T.
PY - 2003/1/24
Y1 - 2003/1/24
N2 - We described previously that during the assembly of the α2β2 heterotetramer of human mitochondrial branched-chain α-ketoacid dehydrogenase (BCKD), chaperonins GroEL/GroES interact with the kinetically trapped heterodimeric (αβ) intermediate to facilitate conversion of the latter to the native BCKD heterotetramer. Here, we show that the 86-kDa heterodimeric intermediate possesses a native-like conformation as judged by its binding to a fluorescent probe 1-anilino-8naphthalene-sulfonate. This large heterodimeric intermediate is accommodated as an entity inside cavities of GroEL and its single-ring variant SR1 and is encapsulated by GroES as indicated by the resistance of the heterodimer to tryptic digestion. The SR1-αβ-GroES complex is isolated as a stable single species by gel filtration in the presence of Mg-ATP. In contrast, an unfolded BCKD fusion protein of similar size, which also resides in the GroEL or SR1 cavity, is too large to be capped by GroES. The cis-capping mechanism is consistent with the high level of BCKD activity recovered with the GroEL-αβ complex, GroES, and Mg-ATP. The 86-kDa native-like heterodimeric intermediate in the BCKD assembly pathway represents the largest protein substrate known to fit inside the GroEL cis cavity underneath GroES, which significantly exceeds the current size limit of 57 kDa established for unfolded proteins.
AB - We described previously that during the assembly of the α2β2 heterotetramer of human mitochondrial branched-chain α-ketoacid dehydrogenase (BCKD), chaperonins GroEL/GroES interact with the kinetically trapped heterodimeric (αβ) intermediate to facilitate conversion of the latter to the native BCKD heterotetramer. Here, we show that the 86-kDa heterodimeric intermediate possesses a native-like conformation as judged by its binding to a fluorescent probe 1-anilino-8naphthalene-sulfonate. This large heterodimeric intermediate is accommodated as an entity inside cavities of GroEL and its single-ring variant SR1 and is encapsulated by GroES as indicated by the resistance of the heterodimer to tryptic digestion. The SR1-αβ-GroES complex is isolated as a stable single species by gel filtration in the presence of Mg-ATP. In contrast, an unfolded BCKD fusion protein of similar size, which also resides in the GroEL or SR1 cavity, is too large to be capped by GroES. The cis-capping mechanism is consistent with the high level of BCKD activity recovered with the GroEL-αβ complex, GroES, and Mg-ATP. The 86-kDa native-like heterodimeric intermediate in the BCKD assembly pathway represents the largest protein substrate known to fit inside the GroEL cis cavity underneath GroES, which significantly exceeds the current size limit of 57 kDa established for unfolded proteins.
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U2 - 10.1074/jbc.M209705200
DO - 10.1074/jbc.M209705200
M3 - Article
C2 - 12431983
AN - SCOPUS:0037462752
SN - 0021-9258
VL - 278
SP - 2515
EP - 2521
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 4
ER -