The following are a selection of protein molecules that highlight different aspects of protein structure
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Haemoglobin
- Haemoglobin is a globular protein responsible for oxygen transport within red blood cells
- It has a quaternary structure made up of four polypeptide subunits (2 alpha subunits and 2 beta subunits)
- Each polypeptide chain is associated with a prosthetic heme group (responsible for oxygen binding)
Aquaporin
- Aquaporins are integral membrane proteins that form channels that allow for the passage of water molecules
- Aquaporins form tetramers in the cell membrane, with each monomer allowing for water movement
- The pores of the aquaporin are impermeable to charged species, thus preventing the passage of ions or solutes
Keratin
- Keratin is a fibrous protein that functions as a key structural material in hair, skin and nails
- Keratin proteins form long twisted strands that may interconnect via disulphide bridges
- Tougher keratin fibres found in hair and nails have more disulphide bridges than more elastic keratin fibres found in skin
Green Fluorescent Protein
- Green fluorescent protein is a fluorophore produced by jellyfish (and commonly used in recombinant DNA experiments)
- The fluorescing chromophore is attached to a central alpha helix, which is surrounded by 11 beta strands forming a barrel
- The tightly packed beta barrel excludes solvent molecules and functions to protect the chromophore from quenching by water
Examples of Protein Structures
