Other Proteins Involved in Subunit Assembly

A third type of protein involved in subunit assembly is a dimerization cofactor of hepatocyte nuclear factor-la, which selectively stabilizes the dimeric structure of the transcription factor necessary for the binding to DNA.57 Although the transcription factor can dimerize on its own in vitro, in vivo assembly is suggested to be regulated by this tissue-specific 11-kDa cofactor protein.57  

Quaternary structure has advantages in potential for flexibility in function and regulation. This seems to be the main reason why so many proteins are oligomeric. It is now generally accepted that oligomeric proteins play a vital role in the overall mechanism of a cell. However, studies on the structural mechanisms by which they fulfill that role were not developed until recently because of the complexity of each oligomeric protein. As described above, recent results have provided valuable insights on the structure-function 

I thank Dr. Yasushi Kawata (Tottori University) and Mr. Tomohiro Mizobata (Kyoto University) for valuable discussions and suggestions. 

Biochem., 58, 111 (1989) see also Chapter 11 in this volume. 

Bauerle, S. A. Ahmed, Methods EnzymoL, 142,398(1987) see also Chapter 7 in this volume. 

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