Sandbox Reserved 994: Difference between revisions

OXA-24 is a monomeric protein with an active site composed of a short α-helix and a β-sheet. The active site of OXA-24 is characterized by a <scene name='69/691536/Oxa24_hydrophobic_active_site/1'>hydrophobic pocket</scene> (shown in pink on the structure) which is representative of Class D β-lactamases as a whole. The active site also contains a hydrophobic <scene name='69/691536/Oxa24_bridge/1'>bridge</scene> which contributes to the substrate specificity for carbapenems and is composed of an arrangement of the Tyr-112 and Met-223 side chains.<ref name="Santillana">Santillana, Elena et al. “Crystal Structure of the Carbapenemase OXA-24 Reveals Insights into the Mechanism of Carbapenem Hydrolysis.” Proceedings of the National Academy of Sciences of the United States of America 104.13 (2007): 5354–5359. PMC. Web. 25 Mar. 2015.</ref> These residues block the active site and only allow a very specific binding configuration of antibiotics. The active site is overall positively charged and contains a sulfate ion along with other solvent molecules when no substrate is bound. The mechanism of attack is through the use of three catalytic residues: Serine-81, Carboxylated Lysine-84, and Serine-128. <scene name='69/691536/Catalytic_residues_oxa24/1'>Catalytic Residues</scene> The hydroxyl chain of Ser-128 conforms in the direction of the active-serine Ser-81, and contributes to the catalytic mechanism.<ref name="Santillana" />