Quaternary structure: assembly of multiple polypeptide subunits
The quarternary structure of hemoglobin
comprises two alpha and
two beta subunits. The
spatial arrangement of each alpha-beta
pair is symmetrical. Contacts between the subunits are by means of H-bonds. The heme groups are inorganic iron (Fe++)
groups that assist in binding oxygen (O2): they are not a typical part of
the quaternary structure of proteins.
Figure © 2000 by Griffiths et al. ; text © 2008 by Steven M. Carr