Globular Proteins Proteins with a compact folded structure (with an interior and exterior), generally containing different types of secondary structure elements as well as irregular regions.

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Globular ProteinsProteins with a compact folded
structure (with an interior and exterior),
generally containing different types of secondary
structure elements as well as irregular regions.
Note the vast majority of proteins are globular.
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Ribbon Diagram Showing Secondary Structures in a
Globular Protein
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Some Globular Protein Structures
Hemoglobin (complex of 4 polypeptide chains or
subunits)
Myoglobin
Triose phosphate isomerase (complex of 2 subunits)
20S Proteasome (complex of 28 subunits)
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Additional Elements of Structure Turns
R2 often Pro
R3 never Pro
Most common type of turn
R2 often Pro
R3 never Pro
??turn
??turns
trans-Pro (above) or cis-Pro (in Type VI ??turns)
often found in turns, but rarely in ??helices and
??sheets.
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Turns with cis-Proline Type VI
Type VIa
Type VIb
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cis-trans Isomerization of Proline Residues
Peptidyl-prolyl cis-trans isomerases accelerate
the isomerization.
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Additional Elements of Structure Loops

• Irregularly structured elements
• More disordered and flexible than turns
• Connects secondary structure elements
• Variable in length and shape
• Frequently form binding sites and enzyme active
  sites

The N- and C-terminal arms of proteins are also
generally more disordered and irregularly
structured.
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Domain and Motifs in Globular Proteins
Supersecondary Structure
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Some Common Motifs Found in Proteins
??hairpin
??? motif
?? motif
? barrels
?? barrel
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