Humboldt State University ® Department of Chemistry

Richard A. Paselk

Chem 431


Fall 2008

Lecture Notes: 22 September

© R. Paselk 2008


3-D Structure of Proteins 3

Super Secondary structures (Motifs)

Recall the two classical structures based on the beta-strand seen above:

Let's next look at some of the other more common motifs found in globular proteins:

Tertiary Structures

The Tertiary structure describes the overall folding of a single covalent structure. With small proteins (< 200 aa residues) the overall structure is generally characterized by an overall tertiary folding with particular secondary structural segments to give particular motifs. Four small proteins are illustrated in your text:

Note that of the four, myoglobin, an intracellular protein, does not have dissulfide bonds, whereas the other three, all extracellular proteins, have dissulfide bonds to stabilize them in their relatively harsh environment.

Note also the presence of alpha-helices and beta-sheets in these proteins (text Table 4-2) to give motifs. Beta-folding patterns, Figure 4-19.

As the number of known protein structures increased, and larger proteins were determined, additional patterns became obvious within the tertiary level of structure: Motifs, which we introduced last time, & Domains.

Pathway Diagrams

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Last modified 23 September 2008