Green Fluorescent Protein: Difference between revisions

===Primary & Secondary Structure===

Green fluorescent protein (<scene name='Green_Fluorescent_Protein/1ema_gfp_default/2'>default scene</scene>) is a 21 kDa protein consisting of 238 residues strung together to form a   

<scene name='Green_Fluorescent_Protein/1ema_gfp_barrel/2'>secondary structure</scene> of five α-helices and one eleven-stranded β-pleated sheet,<ref name="PDBsum" /> where each strand contains nine to thirteen residues each.<ref name="Ormo" />  (To view the primary and secondary structure of GFP, go to [[http://www.ebi.ac.uk/thornton-srv/databases/cgi-bin/pdbsum/GetPage.pl?pdbcode=1ema&template=protein.html&r=wiring&l=1&chain=A www.ebi.aci.uk]].)  These β-strands display an almost “seamless symmetry” in which only two of the strands vary in structural content.<ref name="Phillips">PMID: 9434902</ref>  This β-sheet conforms itself through regular hydrogen bonding into a β-barrel.<ref name="Yang" />  In GFP, the structure is so regular that <scene name='Green_Fluorescent_Protein/Water_stripes/1'>"stripes"</scene> of water molecules (red) can be seen following the structure of the barrel.<ref name="Phillips" />  Together with the α-helices at either end of the molecule, a nearly perfect cylinder is produced, 42Å long and 24Å in diameter,<ref name="Ormo" /> creating what is referred to as a “β-can” formation.<ref name="Phillips" />  The short helical segments at either end of the cylinder form “caps” to further protect the interior of the β-barrel.<ref name="Phillips" />  Overall stability is maintained by this β-can structure, helping to resist unfolding from heat and other denaturants.<ref name="Yang" />