{*Figure 17*}Protein/Enzyme Purification -- Part II
Section B
Protein Characterization
Determine:
1. Native molecular weight (MW)
2. Subunit composition (ie. is the protein a dimer, trimer, tetramer, etc.) by finding subunit MW
3. AA composition (see lecture 5)
4. Enzyme kinetic properties (To be discussed in Part II of this course)
Native Molecular Weight and Subunit Composition.
Some proteins/enzymes are composed of a single polypeptide chain, which are called monomers.
Many have multiple copies of the same polypeptide chain -- homodimers, homotetramers.
Others have more than one polypeptide chain --
for example hemoglobin has an a and b chains with 2 of each to form a heterotetramer.
{*Figure 17*}
List of Native Molecular Weight and Subunit Composition.
Protein/Enzyme ******** MW (daltons) ** # Subunits *** Type
Glucagon ------------------------ 3,000 ----------- 1 ------- Monomer
Insulin -------------------------- 11,500 ----------- 1 ------- Monomer
Cytochrome c ------------------ 13,000 ----------- 1 ------- Monomer
Ribonuclease A ---------------- 13,700 ----------- 1 ------- Monomer
Lysozyme ---------------------- 13,900 ----------- 1 ------- Monomer
Myoglobin --------------------- 16,900 ----------- 1 ------- Monomer
Chymotrypsin ----------------- 21,600 ----------- 1 ------- Monomer
Carbonic Anhydrase ---------- 30,000 ----------- 1 ------- Monomer
Hexokinase ------------------- 102,000 ----------- 2 ------- Dimer
Glycogen Phosphorylase --- 194,000 ----------- 2 ------- Dimer
Hemoglobin ------------------- 64,500 ----------- 4 ------- Tetramer
Lactate Dehydrogenase ----- 140,000 ----------- 4 ------- Tetramer
Pyruvate Dehydrogenase --- 140,000 ----------- 4 ------- Tetramer
Asp Transcarbamoylase ---- 310,000 ---------- 12 ------- Dodecamer
Glutamine Synthetase ------- 600,000 ---------- 12 ------- Dodecamer
©Wilbur H. Campbell, 1995; wcampbel@mtu.edu