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Substrate specificity analysis of protein kinase complex Dbf2-Mob1 by peptide library and proteome array screening
Angie S Mah1, Andrew E H Elia, Geeta Devgan
1Department of Biology, California Institute of Technology, Pasadena, CA 91125, USA. mah@caltech.edu
BMC Biochemistry
|October 26, 2005
Summary
The protein kinase Dbf2-Mob1 phosphorylates substrates with an RXXS motif, crucial for mitotic exit and cytokinesis in yeast. This finding identifies key targets for this essential cell cycle pathway.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- The mitotic exit network (MEN) is vital for cell cycle progression in Saccharomyces cerevisiae.
- Dbf2-Mob1 is a key protein kinase complex within the MEN pathway, implicated in mitotic exit and cytokinesis.
- The specific physiological substrates of Dbf2-Mob1 remain largely uncharacterized.
Purpose of the Study:
- To identify the substrate specificity of the Dbf2-Mob1 protein kinase.
- To discover novel substrates of Dbf2-Mob1 involved in mitotic exit and cytokinesis.
Main Methods:
- Peptide library selection and optimization.
- In vitro phosphorylation assays.
- Phosphosite array and proteome microarray screening.
Main Results:
- Dbf2-Mob1 preferentially phosphorylates serine residues over threonine.
- A specific arginine at the -3 position relative to the serine phosphorylation site (RXXS motif) is required.
- This RXXS motif specificity was confirmed in a proteome-wide analysis of Dbf2-Mob1 substrates.
Conclusions:
- The Dbf2-Mob1 kinase recognizes and phosphorylates substrates containing the RXXS motif.
- Identified potential in vitro substrates enriched for RXXS motifs may mediate MEN functions.
- Dbf2-Mob1 may achieve substrate specificity through docking interactions distinct from the phosphorylation site.