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| Content Provider | PubMed Central |
|---|---|
| Author | Yin, Jun Deng, Zixin Zhao, Guoping Huang, Xi |
| Copyright Year | 2011 |
| Abstract | Cephalosporin acylase (CA) precursor is translated as a single polypeptide chain and folds into a self-activating pre-protein. Activation requires two peptide bond cleavages that excise an internal spacer to form the mature αβ heterodimer. Using Q-TOF LC-MS, we located the second cleavage site between Glu159 and Gly160, and detected the corresponding 10-aa spacer 160GDPPDLADQG169 of CA mutants. The site of the second cleavage depended on Glu159: moving Glu into the spacer or removing 5–10 residues from the spacer sequence resulted in shorter spacers with the cleavage at the carboxylic side of Glu. The mutant E159D was cleaved more slowly than the wild-type, as were mutants G160A and G160L. This allowed kinetic measurements showing that the second cleavage reaction was a first-order, intra-molecular process. Glutaryl-7-aminocephalosporanic acid is the classic substrate of CA, in which the N-terminal Ser170 of the β-subunit, is the nucleophile. Glu and Asp resemble glutaryl, suggesting that CA might also remove N-terminal Glu or Asp from peptides. This was indeed the case, suggesting that the N-terminal nucleophile also performed the second proteolytic cleavage. We also found that CA is an acylpeptide hydrolase rather than a previously expected acylamino acid acylase. It only exhibited exopeptidase activity for the hydrolysis of an externally added peptide, supporting the intra-molecular interaction. We propose that the final CA activation is an intra-molecular process performed by an N-terminal nucleophile, during which large conformational changes in the α-subunit C-terminal region are required to bridge the gap between Glu159 and Ser170. |
| Related Links | http://dx.doi.org/10.1074/jbc.M111.242313 |
| Starting Page | 24476 |
| File Format | |
| ISSN | 1083351X |
| e-ISSN | 1083351X |
| Journal | The Journal of Biological Chemistry |
| Issue Number | 27 |
| Volume Number | 286 |
| Language | English |
| Publisher | American Society for Biochemistry and Molecular Biology |
| Publisher Date | 2011-07-08 |
| Access Restriction | Open |
| Rights Holder | American Society for Biochemistry and Molecular Biology |
| Subject Keyword | Research in Higher Education |
| Content Type | Text |
| Resource Type | Article |
| Subject | Cell Biology Biochemistry Molecular Biology |
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