Bm. Gorovits et al., RHODANESE FOLDING IS CONTROLLED BY THE PARTITIONING OF ITS FOLDING INTERMEDIATES, Biochimica et biophysica acta. Protein structure and molecular enzymology, 1382(1), 1998, pp. 120-128
Rhodanese is used widely as a model for protein folding, since the enz
yme as usually studied refolds poorly unless the process is assisted.
Here, the influence of the partitioning of the folding intermediates o
f bovine rhodanese on the efficiency of its refolding has been investi
gated. Metastable intermediates can be formed during unfolding of the
enzyme. The stabilities of these intermediates and the native protein
with respect to chemical unfolding can be greatly increased by high co
ncentrations of glycerol. The concentration dependence of the protein
folding kinetics indicates that associative processes occur during ren
aturation. It is suggested that, during enzyme refolding, rhodanese un
dergoes fast collapse to an intermediate state I' which partitions to
at least two other states (I '' and I'''). One of these states (I''')
is able to refold to the native enzyme, while the other state (I '') i
s in equilibrium with I' and is prone to slow irreversible aggregation
Stabilization of I '' against irreversible aggregation by glycerol re
sults in increased yield of the protein refolding and a complex temper
ature dependence of the protein renaturation. The nature of the I '' t
ype intermediate has been investigated. Based on the fact that extensi
ve hydrophobic surfaces are exposed during formation of the intermedia
tes, it is suggested that partial dissociation of the two structural d
omains of rhodanese is an early event in unfolding. Interactions of di
fferent folding intermediates of rhodanese with the chaperonin GroEL w
ere investigated, and the results suggest that the more extensively un
folded intermediates bind tighter than those that appear later on the
rhodanese refolding pathway. (C) 1998 Elsevier Science B.V.