Article

Capture of monomeric refolding intermediate of human muscle creatine kinase.

Department of Biochemistry and Molecular Biology, Beijing Normal University, Beijing Key Laboratory, PR China.
Protein Science (impact factor: 2.8). 02/2006; 15(1):171-81. DOI:10.1110/ps.051738406 pp.171-81
Source: PubMed

ABSTRACT Human muscle creatine kinase (CK) is an enzyme that plays an important physiological role in the energy metabolism of humans. It also serves as a typical model for studying refolding of proteins. A study of the refolding and reactivation process of guanidine chloride-denatured human muscle CK is described in the present article. The results show that the refolding process can be divided into fast and slow folding phases and that an aggregation process competes with the proper refolding process at high enzyme concentration and high temperature. An intermediate in the early stage of refolding was captured by specific protein molecules: the molecular chaperonin GroEL and alpha(s)-casein. This intermediate was found to be a monomer, which resembles the "molten globule" state in the CK folding pathway. To our knowledge, this is the first monomeric intermediate captured during refolding of CK. We propose that aggregation is caused by interaction between such monomeric intermediates. Binding of GroEL with this intermediate prevents formation of aggregates by decreasing the concentration of free monomeric intermediates, whereas binding of alpha(s)-casein with this intermediate induces more aggregation.

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Keywords

aggregates
 
aggregation process competes
 
CK folding pathway
 
energy metabolism
 
enzyme concentration
 
first monomeric intermediate
 
free monomeric intermediates
 
guanidine chloride-denatured human muscle CK
 
intermediate induces
 
molecular chaperonin GroEL
 
monomeric intermediates
 
physiological role
 
proper refolding process
 
proteins
 
reactivation process
 
refolding
 
refolding process
 
slow folding phases
 
specific protein molecules
 
typical model
 

Sen Li