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- PubMed Abstract:
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Lipscomb, W.N.,Hartsuck, J.A.,Reekejunior, G.N.,Quiocho, F.A.,Bethge, P.H.,Ludwig, M.L.,Steitz, T.A.,Muirhead, H.,Coppola, J.C.
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- Refined Crystal Structure of Carboxypeptidase a at 1.54 Angstroms Resolution.
Rees, D.C.,Lewis, M.,Lipscomb, W.N.
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Quiocho, F.A.,Lipscomb, W.N.
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Rees, D.C.,Lipscomb, W.N.
(1981) Proc.Natl.Acad.Sci.USA 78: 5455
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Rees, D.C.,Lewis, M.,Honzatko, R.B.,Lipscomb, W.N.,Hardman, K.D.
(1981) Proc.Natl.Acad.Sci.USA 78: 3408
- Crystallographic Studies on Apocarboxypeptidase a and the Complex with Glycyl-L-Tyrosine
Rees, D.C.,Lipscomb, W.N.
(1983) Proc.Natl.Acad.Sci.USA 80: 7151
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A high-resolution x-ray crystallographic investigation of the complex between carboxypeptidase A (CPA; peptidyl-L-amino-acid hydrolase, EC 188.8.131.52) and the slowly hydrolyzed substrate glycyl-L-tyrosine was done at -9 degrees C. Although this enzyme- ...
A high-resolution x-ray crystallographic investigation of the complex between carboxypeptidase A (CPA; peptidyl-L-amino-acid hydrolase, EC 184.108.40.206) and the slowly hydrolyzed substrate glycyl-L-tyrosine was done at -9 degrees C. Although this enzyme-substrate complex has been the subject of earlier crystallographic investigation, a higher resolution electron-density map of the complex with greater occupancy of the substrate was desired. All crystal chemistry (i.e., crystal soaking and x-ray data collection) was performed on a diffractometer-mounted flow cell, in which the crystal was immobilized. The x-ray data to 1.6-A resolution have yielded a well-resolved structure in which the zinc ion of the active site is five-coordinate: three enzyme residues (glutamate-72, histidine-69, and histidine-196) and the carbonyl oxygen and amino terminus of glycyl-L-tyrosine complete the coordination polyhedron of the metal. These results confirm that this substrate may be bound in a nonproductive manner, because the hydrolytically important zinc-bound water has been displaced and excluded from the active site. It is likely that all dipeptide substrates of carboxypeptidase A that carry an unprotected amino terminus are poor substrates because of such favorable bidentate coordination to the metal ion of the active site.