Section 11 - Quaternary Structure
Index to Course Material
To best appreciate the material in this chapter, you should have your WWW
browser configured to invoke RasMol as the helper application for chemical
MIME type files.
This material includes some RasMol scripts, which may be copied directly
into the RasMol command line from your browser window; alternatively download
the script files and use the RasMol script command to execute them.
Literally, quaternary is subsequent to tertiary. In the context of
biology, quaternary structures, such as enzymes, are assemblies of
tertiary structural units, such as proteins. The assembly of
bio-molecules into quaternary structures provides enhanced, multiple or
novel functional roles. These assemblies may contain as few as two
units, as in an enzyme complex, or hundreds, as in a virus. Often quaternary
structure is organized symmetrically. This allows the formation
of large complexes with only a few different tertiary units. In
multiple unit (multimeric) complexes the single units (monomers) form
contacts between each other. In some cases, the monomer must change its
conformation in order to make these contacts. Insulin illustrates how
the tertiary structure can be influenced by the quaternary
organizational requirements. Enzymes exemplify the advantages of
multimeric complexes that combine different functions. Multiple functionality is
enhanced by forming multi-enzyme complexes. Finally, large assemblies
play not only functional but structural roles on the cellular level.
While studying this section, bear in mind the interplay between tertiary
and quaternary structure. For instance, consider the question of the definition
of quaternary structure- is it an arbitrary classification? Also
consider the advantages, both functional and structural, that are provided by
the assemblies of tertiary structures.
Please e-mail any questions or comments on the topics of the current course material to
the pps96-proteins list.
Thanks to
Index to Course Material
John Kenney, John Walshaw
Last updated 4th Jul '96