2bd7: Difference between revisions

[[Image:2bd7.gif|left|200px]]<br /><applet load="2bd7" size="350" color="white" frame="true" align="right" spinBox="true"  

Mass spectrometric screening reveals that an unmodified natural heptapeptide--human beta-casomorphin-7, an internal sequence of human beta-casein that possesses opioid-like activity--reacts with porcine pancreatic elastase to form an unusually stable acyl-enzyme complex at low pH. X-ray crystallographic analysis (to 1.9 A resolution) at pH 5 shows continuous electron density linking the C-terminal isoleucine of beta-casomorphin-7 to Ser 195 through an ester bond. The structure reveals a well defined water molecule (Wat 317), equidistant between the carbon of the ester carbonyl and N epsilon 2 of His 57. Deprotonation of Wat 317 will produce a hydroxide ion positioned to attack the ester carbonyl through the favoured Burgi-Dunitz trajectory.

2BD7 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Sus_scrofa Sus scrofa] with <scene name='pdbligand=CA:'>CA</scene>, <scene name='pdbligand=SO4:'>SO4</scene>, <scene name='pdbligand=ARG:'>ARG</scene> and <scene name='pdbligand=PHE:'>PHE</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Pancreatic_elastase Pancreatic elastase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.4.21.36 3.4.21.36] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2BD7 OCA].  

[[Category: Schofield, C J.]]

[[Category: Wilmouth, R C.]]

''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 16:36:32 2008''