Chiravuri, M., Lee, H., Mathieu, S.L. and Huber, B.T. (2000) Homodimerization via a Leucine Zipper Motif Is Required for Enzymatic Activity of Quiescent Cell Proline Dipeptidase. Journal of Biological Chemistry, 275 (35). pp. 26994-26999. ISSN 1083-351X
Quiescent cell proline dipeptidase (QPP) is an intracellular serine protease that is also secreted upon cellular activation. This enzyme cleaves N-terminal Xaa-Pro dipeptides from proteins, an unusual substrate specificity shared with dipeptidyl peptidase IV (CD26/DPPIV). QPP is a 58-kDa protein that elutes as a 120-130-kDa species from gel filtration, indicating that it forms a homodimer. We analyzed this dimerization with in vivo co-immunoprecipitation assays. The amino acid sequence of QPP revealed a putative leucine zipper motif, and mutational analyses indicated that this leucine zipper is required for homodimerization. The leucine zipper mutants showed a complete lack of enzymatic activity, suggesting that homodimerization is important for QPP function. On the other hand, an enzyme active site mutant retained its ability to homodimerize. These data are the first to demonstrate a role for a leucine zipper motif in a proteolytic enzyme and suggest that leucine zipper motifs play a role in mediating dimerization of a diverse array of proteins.
|Institution:||The University of Sheffield|
|Academic Units:||The University of Sheffield > University of Sheffield Research Centres and Institutes > The Krebs Institute for Biomolecular Research (Sheffield)|
|Depositing User:||Sherpa Assistant|
|Date Deposited:||21 Oct 2009 11:17|
|Last Modified:||21 Oct 2009 11:17|
|Publisher:||American Society for Biochemistry and Molecular Biology|