BCEM 393 Lecture Notes - Lecture 6: Heterotetramer, Proteolysis, Hemoglobin
29 May 2018
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Tertiary Structures
PRINCIPLES OF TERTIARY STRUCTURE
- Principle #1 — residues far apart the primary structure pack together in the folded protein
- Myoglobin is a 153-residue protein that binds oxygen. The iron atom in the heme group is
critical for this role
- The heme group is a prosthetic group (ie. tightly bound cofactor)
- Cofactors have 2 subsets: coenzyme and prosthetic group
- Secondary structures were held together mainly by hydrogen bonding between carbon
backbones
- Principle #2 — hydrophobic amino acid residues tend to pack on the interior of globular
proteins. Hydrophilic residues tend to be on the outside surface
- Globular porteins are soluble
- An exception are two histidine residues that are important for binding the heme iron and
oxygen
- Principle #3 — tertiary structure is mainly held together by interactions between side chains:
hydrophobic interactions, ionic interactions, and (to a lesser extent) hydrogen bonds are
involved. Also, sometimes, by intrachain disulfide linkages (-S-S-)
- A disulphide linkage is a covalent bond that is not seen in secondary structures
- Principle #4 — Elements of secondary structure can come together to form motifs. A motif
often has particular function (eg. the helix-turn-helix is a DNA-binding motif)
- A motif is a super secondary structure, which is not int he tertiary structure, but gives more
info than a typical secondary structure
- Principle #5 — Some proteins fold into more than one compact region. Each is called a
domain (some proteins don't have any domains). The cell-surface protein CD4 has four
domains
INTEGRAL MEMBRANE PROTEINS HAVE SPECIAL TERTIARY STRUCTURES (USUALLY A
BUNDLE OF HELICES)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Principle #1 residues far apart the primary structure pack together in the folded protein. Myoglobin is a 153-residue protein that binds oxygen. The iron atom in the heme group is critical for this role. The heme group is a prosthetic group (ie. tightly bound cofactor) Cofactors have 2 subsets: coenzyme and prosthetic group. Secondary structures were held together mainly by hydrogen bonding between carbon backbones. Principle #2 hydrophobic amino acid residues tend to pack on the interior of globular proteins. Hydrophilic residues tend to be on the outside surface. An exception are two histidine residues that are important for binding the heme iron and oxygen. Principle #3 tertiary structure is mainly held together by interactions between side chains: hydrophobic interactions, ionic interactions, and (to a lesser extent) hydrogen bonds are involved. A disulphide linkage is a covalent bond that is not seen in secondary structures. Principle #4 elements of secondary structure can come together to form motifs.
