The cytosolic carboxypeptidases CCP2 and CCP3 catalyze posttranslational removal of acidic amino acids.
Bottom Line: Here we complete the functional characterization of this protein family by demonstrating that CCP2 and CCP3 are deglutamylases, with CCP3 being able to hydrolyze aspartic acids with similar efficiency.In addition, we show that CCP2 and CCP3 are highly regulated proteins confined to ciliated tissues.The characterization of two novel enzymes for carboxy-terminal protein modification provides novel insights into the broadness of this barely studied process.
Affiliation: Institut de Biotecnologia i de Biomedicina, Department of Biochemistry and Molecular Biology, Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona), Spain Institut Curie, 91405 Orsay, France.Show MeSH
Mentions: After the discovery that four (CCP1, CCP4, CCP5, CCP6) of the six murine CCPs are deglutamylases (Rogowski et al., 2010), attention turned to the potential functions of CCP2 and CCP3. Considering that enzymes for deglycylation and detyrosination of tubulin have not been identified so far and that the reverse enzymes for these two reactions are all members of the same TTLL family, one expectation was that CCP2 and CCP3 could be involved in either or both of these PTMs. Indeed, an initial report (Sahab et al., 2011) attributed a detyrosinating activity to CCP2; however, unambiguous evidence for this activity was not provided, and overexpression of CCP2 did not lead to a strong increase in detyrosinated tubulin. To gain more insight into the substrate preferences of CCP2 and CCP3, we modeled the catalytic domains of the two enzymes based on the CCP crystal structures of Pseudomonas aeruginosa (PDB 4a37; Otero et al., 2012), Burkholderia mallei (PDB 3k2k), and Shewanella denitrificans (PDB 3l2n; Figure 1A and Supplemental Figure S1A).
Affiliation: Institut de Biotecnologia i de Biomedicina, Department of Biochemistry and Molecular Biology, Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona), Spain Institut Curie, 91405 Orsay, France.