Effects of pH on the Structure and Function of Carboxypeptidase A: Crystallographic Studies
- Creators
- Shoham, G.
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Rees, D. C.
- Lipscomb, W. N.
Abstract
High-resolution crystal structures are described for carboxypeptidase A (EC 3.4.17.1) in crystals grown at pH 8.5, 9.0, and 9.5 and compared with the structure at pH 7.5. The comparison shows that in the pH range of 7.5-9.5 the enzyme structure is practically unchanged, and, most importantly, that the flexible side chain of Tyr-248 remains exclusively in the "up" position, away from the Zn atom, throughout the pH range. There is no evidence for binding of Tyr-248 to Zn at any of these pH values. We conclude that the interaction of Tyr-248 with Zn is not an essential part of the mechanism of carboxypeptidase A and that its occurrence is an artifact of chemical modification of Tyr-248. It is also suggested that Tyr-248 is not uniquely associated with the observed high pK of the enzymatic hydrolysis.
Additional Information
© 1984 National Academy of Sciences. Contributed by W. N. Lipscomb, August 27, 1984. We are grateful to Drs. R. B. Honzatko, M. Lewis, L. C. Kuo, and W. Bennett for helpful discussion and experimental assistance. We thank the National Institutes of Health (GM 06920) for support and the National Science Foundation (PCM-77-11398) for the computational facilities. The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.Attached Files
Published - 23_shoham_1984.pdf
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Additional details
- PMCID
- PMC392233
- Eprint ID
- 54641
- Resolver ID
- CaltechAUTHORS:20150210-094928604
- NIH
- GM 06920
- NSF
- PCM-77-11398
- Created
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2015-02-11Created from EPrint's datestamp field
- Updated
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2019-10-03Created from EPrint's last_modified field