title: A structural and functional dissection of the cardiac stress response factor MS1.
abstract: MS1 is a protein predominantly expressed in cardiac and skeletal muscle that is upregulated in response to stress and contributes to development of hypertrophy. In the aortic banding model of left ventricular hypertrophy, its cardiac expression was significantly upregulated within 1 h. Its function is postulated to depend on its F-actin binding ability, located to the C-terminal half of the protein, which promotes stabilization of F-actin in the cell thus releasing myocardin-related transcription factors to the nucleus where they stimulate transcription in cooperation with serum response factor. Initial attempts to purify the protein only resulted in heavily degraded samples that showed distinct bands on SDS gels, suggesting the presence of stable domains. Using a combination of combinatorial domain hunting and sequence analysis, a set of potential domains was identified. The C-terminal half of the protein actually contains two independent F-actin binding domains. The most C-terminal fragment (294-375), named actin binding domain 2 (ABD2), is independently folded while a proximal fragment called ABD1 (193-296) binds to F-actin with higher affinity than ABD2 (KD 2.21 ± 0.47 μM vs. 10.61 ± 0.7 μM), but is not structured by itself in solution. NMR interaction experiments show that it binds and folds in a cooperative manner to F-actin, justifying the label of domain. The architecture of the MS1 C-terminus suggests that ABD1 alone could completely fulfill the F-actin binding function opening up the intriguing possibility that ABD2, despite its high level of conservation, could have developed other functions.
authors.affiliation: Department of Biochemistry, University of Leicester, Leicester LE1 9HN, United Kingdom.
authors.forename: Claudia
authors.initials: C
authors.lastname: Fogl
authors.forename: Loretto
authors.initials: L
authors.lastname: Puckey
authors.forename: Ulrike
authors.initials: U
authors.lastname: Hinssen
authors.forename: Mariola
authors.initials: M
authors.lastname: Zaleska
authors.forename: Mohammed
authors.initials: M
authors.lastname: El-Mezgueldi
authors.forename: Rebecca
authors.initials: R
authors.lastname: Croasdale
authors.forename: Andrew
authors.initials: A
authors.lastname: Bowman
authors.forename: Akira
authors.initials: A
authors.lastname: Matsukawa
authors.forename: Nilesh J
authors.initials: NJ
authors.lastname: Samani
authors.forename: Renos
authors.initials: R
authors.lastname: Savva
authors.forename: Mark
authors.initials: M
authors.lastname: Pfuhl
mesh_terms: D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D001665:Binding Sites; D002942:Circular Dichroism; D017124:Conserved Sequence; D008840:Microfilament Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D019906:Nuclear Magnetic Resonance, Biomolecular; D017510:Protein Folding; D055550:Protein Stability; D017434:Protein Structure, Tertiary
chemical_list: C461039:Abra protein, rat; D000199:Actins; D008840:Microfilament Proteins