Novel perspectives of target-binding by the evolutionarily conserved PP4 phosphatase

Area of Science:

• Molecular Biology
• Biochemistry
• Cell Biology

Background:

• Protein phosphatase 4 (PP4) is a crucial eukaryotic enzyme regulating cell division, development, and DNA repair.
• The PP4c-R2-R3 complex is the primary form of PP4, with the R3 subunit's EVH1 domain mediating substrate recognition.
• Canonical EVH1 domains typically bind proline-rich sequences via conserved aromatic residues.

Purpose of the Study:

• To identify novel binding partners of the Drosophila PP4 R3 subunit (Falafel) EVH1 domain.
• To characterize the substrate recognition mechanism of the Falafel EVH1 domain.
• To investigate the role of the Smk-1 domain in Falafel's target binding.

Main Methods:

• Identification of binding partners for the Falafel EVH1 domain.
• Biochemical assays to confirm interactions with identified motifs.
• Analysis of conserved residues within the EVH1 domain.

Main Results:

• The Falafel EVH1 domain recognizes atypical FxxP and MxPP motifs, not proline-rich sequences.
• A conserved leucine residue in Falafel's EVH1 domain is critical for this novel binding.
• The Smk-1 domain of Falafel is implicated in target binding.

Conclusions:

• The PP4 EVH1 domain represents a new class of EVH1 family members capable of binding low-proline content sequences.
• These findings reveal a novel substrate-recognition mechanism for PP4, enhancing understanding of its function.
• The study provides insights into the evolutionary adaptability of EVH1 domains.