A 639 substitution (Highlighted in Red) of Asp for Tyr in 1S0V (T7 RNA Polymerase) results in a
dramatic drop of enzymatic activity. One would expect this decrease to be a result of a
alternation in the polymerase to bind to ATP. This matters because RNA Polymerase is ATP
dependent.
A unit of symmetry that can be reflected and mirrored defines hemoglobin’s 4 monomeric
regions. Of these four polypeptide chain units, two are alpha and two are beta units. Although
the alpha and beta chains have different sequences of aa, they fold to form a similar 3D
structure. From looking at each unit’s relation to each other, it’s becomes clear that only
noncovalent interactions hold the four chains together. Myoglobins unit does not have a shape
that is unique in this fashion, thus it cannot associate with other forms to have a larger
tetrameric structure.
Noncovalent interactions hold the hemoglobin’s chains together.