Which of the following statement characterize both Hemoglobin and Myoblogin -
Heme lies in the hydrophobic interior (pocket) of globin chain of hemoglobin and myoglobin.
Polypeptide chain of myoglobin and all four polypeptide chains of hemoglobin have helical structure.
Polypeptide subunits of hemoglobin are held together by hydrogen bonds, salt (ionic) bonds and Van der walls forces. Myoglobin has only one polypeptide chain, thus there is no question of bonding between subunits.
However, this should not be confused that there is no bonds in myoglobin. Myoglobin has secondary and tertiary structure which are stabilized by non-covalent bonds. Polypeptide chain of myoglobin is compactly folded so that the non-polar (hydrophobic) amino acids lies in the interior forming hydrophobic bonds and polar (hydrophilic) amino acid on the exterior surface forming hydrogen and electrostatic (ionic bonds). So, compact structure of myoglobin is stabilized by hydrogen and ionic bonds as well as by the hydrophobic interactions.
Similarly, Each polypeptide chain of hemoglobin is stabilized by hydrophobic bonds (in interior) and hydrogen and ionic (electrostatic) bonds (on exterior).
Thus :-
Stabilization of polypeptide chain itself of hemoglobin and myoglobin → hydrogen bonds, electrostatic (ionic) bonds and hydrophobic bonds.
Subunits (4 polypeptide chains) of hemoglobin are held together by → hydrogen bonds, electrostatic bonds and Van der walls forces.
A hemoglobin molecule binds 4 molecules of O2 and a myoglobin molecule binds 1 molecule of O2
Each hemoglobin molecule has 4 heme groups and myoglobin has one heme group.
Non-helical
Subunits which are held together by hydrogen bonds
Binds with 2 Heme
Heme at hydrophobic pockets