Protein interactions. Aggregation of globular proteins

Many globular proteins are known to polymerize. It is pointed out that a monomer molecule containing a single polypeptide chain is asymmetric, and that a single of complementary combining regions on such a molecule would permit it to attach to equivalent molecules in such a way as to form a helical structure, giving rise to . If the pitch of the helix is zero or nearly zero the helix degenerates into a circle, a small polymer (dimer, trimer) is formed. A reasonable amount (about 5°) of freedom angular motion in the bond between adjacent molecules would permit a helical fibril large diameter to change its length by as much as a factor of two, and would also permit aggregates with walls one, two, or three molecules thick to be formed. It is that some of the observed properties of globular proteins can be accounted for this way.