A novel cochaperonin that modulates the ATPase activity of cytoplasmic chaperonin.
The folding of alpha- and beta-tubulin requires three proteins: the heteromeric TCP-1-containing cytoplasmic chaperonin and two additional protein cofactors (A and B). We show that these cofactors participate in the folding process and do not merely trigger release, since in the presence of Mg-ATP alone, alpha- and beta-tubulin target proteins are discharged from cytoplasmic chaperonin in a nonnative form. Like the prokaryotic cochaperonin GroES, which interacts with the prototypical Escherichia coli chaperonin GroEL and regulates its ATPase activity, cofactor A modulates the ATPase activity of its cognate chaperonin. However, the sequence of cofactor A derived from a cloned cDNA defines a 13-kD polypeptide with no significant homology to other known proteins. Moreover, while GroES functions as a heptameric ring, cofactor A behaves as a dimer. Thus, cofactor A is a novel cochaperonin that is structurally unrelated to GroES.
Gao
Y
Y
Department of Biochemistry, New York University Medical Center, New York 10016.
Melki
R
R
Walden
P D
PD
Lewis
S A
SA
Ampe
C
C
Rommelaere
H
H
Vandekerckhove
J
J
Cowan
N J
NJ
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D018833:Chaperonins; D046911:Macromolecular Substances; D051379:Mice; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D014404:Tubulin / Q000737:chemistry / Q000378:metabolism
D046911:Macromolecular Substances; D011506:Proteins; D014404:Tubulin; C087414:chaperonin cofactor A; D000251:Adenosine Triphosphatases; D018833:Chaperonins