Protein Structure 2 Higher Order Protein Structures

Hierarchy of Protein Structure Primary sequence Primary sequence- The amino acid sequence of a polypeptide, listed from N-terminus to C-terminus. Secondary structure Secondary structure- Recurring structural feature of proteins stabilized exclusively by hydrogen bonds between peptide bond elements. Supersecondary structure Supersecondary structure- Recurring structural feature of proteins composed of two or more secondary structural elements. Domain- Domain- A segment of protein structure that is autonomously stable. Tertiary structure Tertiary structure- A stable, independent protein encoded by a single gene. Quaternary structure Quaternary structure- A complex structure composed of two or more tertiary structure subunits.

Alpha-fibrous proteins: Coiled-coil Helix Supersecondary Structure Heptad repeats in GCN4 Four-helical bundle

Sequence Comparison Reveals Positional Preference Within Heptad Repeats

Max1 as an Example of a Leucine Zipper Motif Protein

Parallel and Anti-parallel Beta Sheets anti-parallel parallel

 Supersecondary Structures Structure of  -grasp fold of ubiquitin showing  motif Repeating  motifs (n=7) form a Rossmann fold structure

 Supersecondary Structures Greek key motif Beta meander motif

 -coil-  Supersecondary Structure IpaH3.0

Domains and Tertiary Structure Domains- Structurally autologous structures possessing discrete functions that comprises part of the tertiary structure (beads on a string). Domains can be identified by their characteristic sequences. Ex: DNA binding domains, NAD + /NADP + binding domains, HECT domains, Zn finger domains, etc. Motif- A highly conserved, short amino acid sequence that identifies a discrete function. Ex: Protein kinase phosphorylation motifs, Ca++ binding motifs, etc. Pyruvate kinase domain structure

Quaternary Structure