User:Wally Novak/Sandbox Hicks: Difference between revisions

<scene name='74/744126/Pcna_monomer_helixfront_2/1'> The PCNA monomers </scene> consist of 258 residues each and are a mass of 28.916 kDa. Each monomer contributes two domains to the trimeric ring. These domains possess anti-parallel beta sheets (blue) which approach each other on one end, but are separated by two alpha helices at the other (red), creating a 45 degree wedge in the sheets with alpha helices at the blunt end. The domains are connected by an extended beta sheet. This creates a <scene name='74/744126/6_fold_symmetry/1'> six-fold symmetry within the trimeric ring </scene> and it also creates a β-α-β-β-β motif going around the ring. <ref>PMID:8001157</ref>  

== Interactions with DNA ==

Other structural features of PCNA elucidate how it functions as a sliding clamp protein, and how PCNA is able to loosely interact with DNA. Firstly, b-DNA and a-DNA have cross sectional diameters of about 18 and 21 Angstroms. PCNA has an internal diameter of approximately 34 Angstroms. [3] The diameter of PCNA being a little less than twice the size of the two most common forms of DNA suggests that size of the clamp plays a role in how tightly it associates with DNA. Specifically, if the difference in diameters was were greater, there would be little association, but if it were smaller, there would be a tighter association, which would not allow for the "sliding" of the sliding clamp.

 

 

PCNA also has many <scene name='74/744126/Acidic_residues_pcna/1'>has a large number of acidic residues</scene>