Molecular and Cellular Biochemistry

, Volume 262, Issue 1, pp 187-193

First online:

Ribosomal protein S18 identified as a cofilin-binding protein by using phage display library

  • Kaoru KusuiAffiliated withNational Institute of Health Sciences
  • , Haruyo SasakiAffiliated withNational Institute of Health Sciences
  • , Reiko AdachiAffiliated withNational Institute of Health Sciences
  • , Sachiko MatsuiAffiliated withNational Institute of Health SciencesKyoritsu College of Pharmacy
  • , Kazuo YamamotoAffiliated withGraduate School of Frontier Sciences, University of Tokyo
  • , Teruhide YamaguchiAffiliated withNational Institute of Health Sciences
  • , Tadashi KasaharaAffiliated withKyoritsu College of Pharmacy
  • , Kazuhiro SuzukiAffiliated withNational Institute of Health Sciences

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We previously reported that an actin-binding protein, cofilin, is involved in superoxide production, phagocytosis, and chemotaxis in activated phagocytes through cytoskeletal reorganization. To elucidate the functions of cofilin in greater detail we tried to identify cofilin-binding proteins by using a phage-displayed cDNA library constructed from human brain mRNAs. Several phage clones capable of binding to cofilin were obtained, and the phage with the strongest binding affinity contained the C-terminal half of ribosomal protein S18. To confirm the interaction between the S18 protein and cofilin, we investigated whether cofilin would bind to His-tagged S18 protein immobilized in Ni-NTA-agarose gel. Cofilin and the S18 protein co-eluted with a low pH (4.5) buffer, suggesting that the proteins interact with each other. Preincubation of cofilin with actin abrogated the binding to protein S18, indicating that cofilin interacts with S18 protein at the actin-binding site, and cofilin co-immunoprecipitated with FLAG-tagged S18 protein expressed in COS-7 cells. These results suggest that some cofilin molecules bind the ribosomal S18 protein under physiological conditions. (Mol Cell Biochem 262: 187–193, 2004)

actin cofilin phage display ribosomal protein S18