Atragin: Difference between revisions

<scene name='Atragin/M_domain/1'>six alpha-helixes and 5 beta-sheets</scene> and is a metalloendopeptidase. Every endometalloprotease contains a <scene name='Atragin/Metalloph-h/1'>HEXXHXXGXXH</scene> strain of residues needed for zinc and substrate binding for proteolysis. In Atragin, the binding sequence can be found from aa 341-351. The <scene name='Atragin/Zn/1'>zinc</scene> atom is ligated by the side chains of His341 and 345 on the a-helix, and this allows His 351 at the turn the be responsible for the catalytic reaction <ref name=Gomis-Ruth>PMID: 12746556</ref>.  

One of the ways that the N. atra is able to prevent self-proteolysis is by storing the atragrin protein in a venom lumen gland at an acidic pH and containing citrate and the tripeptide pyroglutamyl-lysyl-tryptophan enzymatic inhibitor in the gland<ref name=Guan>PMID: 19932752</ref><ref name=Odell>PMID: 9839664</ref><ref name=Marques-porto>PMID: 18325841</ref>. In acidic conditions, there is no detectable electron density at the flexible loop, which contains the Met-turn. Under acidic conditions, the prononated histidines cause a structural change which results in an unfixed position of the zinc atom <ref name=Guan>PMID: 19932752</ref>. The picture below shows the general movement of the histidines.

[[Image:Ph_difference.jpg]] <ref name=Guan>PMID: 19932752</ref>