Creatine kinase monomers

When p-strands, p-pleated sheets and a-helices fold together they form the tertiary structure of the protein, for example the creatine kinase monomers CK-M and CK-B (Fig. 8.1). 

Grossman, S.H., Pyle, J., and Steiner, R.J. (1981) Kinetic evidence for active monomers during the reassembly of denatured creatine kinase. Biochemistry 21, 6122. 

Some enzymes, such as yeast hexokinase and creatine kinase (Chapter 12), associate in extremely asymmetric ways.102 A dimer is formed by means of heterologous interactions but steric hindrance prevents the unsatisfied sets of interacting groups from joining with additional monomers to form higher polymers. 

Creatine kinase is a dimer (molecular weight 82 000), with an active site on each monomer. The activating metal binds to the ATP only, i.e. type I. Spin labelling of the cysteine residue at the active site has allowed distance measurements to Mnu. It appears that Mn remains bound to the a- and /3-phosphoryl groups in ADP. 

Figure 8.2 Quaternary structure. The two different creatine kinase (CK) monomers (M and B) associate to form three different dimers the homo-dimers CK-MM (found in skeletal muscle) and CK-BB (brain), and the hetero-dimer CK-MB (which is abundant in cardiac muscle).

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