GroEL has a greater affinity for the mitochondrial isozyme (mAAT) of aspart
ate aminotransferase than for its cytosolic counterpart (cAAT) (Mattingly J
R Jr, Iriarte A, Martinez-Carrion M, 1995, J Biol Chern 270:1138-1148), two
proteins that share a high degree of sequence similarity and an almost ide
ntical spatial structure. The effect of detergents on the refolding of thes
e large, dimeric isozymes parallels this difference in behavior. The presen
ce of non-ionic detergents such as Triton X-100 or lubrol at concentrations
above their critical micelle concentration (CMC) interferes with reactivat
ion of mAAT unfolded in guanidinium chloride but increases the yield of cAA
T refolding at low temperatures. The inhibitory effect of detergents on the
reactivation of mAAT decreases progressively as the addition of detergents
is delayed after starting the refolding reaction. The rate of disappearanc
e of the species with affinity for binding detergents coincides with the sl
owest of the two rate-limiting steps detected in the refolding pathway of m
AAT. Limited proteolysis studies indicate that the overall structure of the
detergent-bound mAAT resembles that of the protein in a complex with GroEL
. The mAAT folding intermediates trapped in the presence of detergents can
resume reactivation either upon dilution of the detergent below its CMC or
by adding beta-cyclodextrin. Thus, isolation of otherwise transient product
ive folding intermediates for further characterization is possible through
the use of detergents.