2bb4
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| , resolution 1.600Å | |||||||
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| Ligands: | , , and | ||||||
| Activity: | Pancreatic elastase, with EC number 3.4.21.36 | ||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||
Porcine pancreatic elastase complexed with beta-casomorphin-7 and Asp-Phe at pH 5.0
OverviewOverview
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.
About this StructureAbout this Structure
2BB4 is a Single protein structure of sequence from Sus scrofa. Full crystallographic information is available from OCA.
ReferenceReference
Structure of a specific acyl-enzyme complex formed between beta-casomorphin-7 and porcine pancreatic elastase., Wilmouth RC, Clifton IJ, Robinson CV, Roach PL, Aplin RT, Westwood NJ, Hajdu J, Schofield CJ, Nat Struct Biol. 1997 Jun;4(6):456-62. PMID:9187653
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