GLOBULAR ACTIN IS THE PARTIALLY INTRINSICALLY DISORDERED PROTEIN WITH QUASI-STATIONARY STRUCTURE
O.I. Povarova,1,* Yu.A. Gagarskaia,1,2 V.N. Uversky,1,3,4 I.M. Kuznetsova,1 K.K. Turoverov 1,2
1 Institute of Cytology RAS, St. Petersburg, 194064,
2 Peter the Great St. Petersburg State Polytechnical University, 194064,
3 Department of Molecular Medicine and USF Health Byrd Alzheimer’s Research Institute,
Morsani College of Medicine, University of South Florida, Tampa, FL, USA, 33620-5550,
and 4 Institute for Biological Instrumentation, RAS, Pushchino, 142290;
* e-mail: olp@incras.ru
It is shown that the native globular actin (G-actin) is the thermodynamically unstable (quasi-stationary)
form of the protein. This state is stabilized by Mg2+ (in vitro replaced by Ca2+). In vivo this state occurs as a result
of complex energy-consuming post-translational folding processes including chaperone Hsp70, prefoldin
and CCT complex, providing the formation of the native structure stabilized by Ca2+ and ATP. Structures formed
by actin polypeptide chain constantly form complexes with their partners (chaperones Hsp70, prefoldin
and chaperonin CCT in folding process, with an Mg ion and ATP in the native state, with numerous actin-binding
proteins during the formation and functioning of the cell cytoskeleton, with myosin and other proteins of
the muscle contraction in the muscle cells). Actin denaturation is accompanied by self-association of molecules,
so the inactivated actin is the thermodynamically stable compact structure consisting of 14—16 protein molecules.
Apparently, proteins with quasi-stationary native state are widespread in nature. The emergence of these
states is energy-consuming and is conjugated with the inability of the polypeptide chain to form the native
compact structure without assistants (complex machinery of protein folding in the cell) and without interaction
with their natural partners, in particular with metal ions.
Key words:
actin, folding, native structure, aggregation, inactivated actin, quasi-stationary state, intrinsically disordered proteins
| Back
| Contents
| Main |
|
