title: A second look at mini-protein stability: analysis of FSD-1 using circular dichroism, differential scanning calorimetry, and simulations.
abstract: Mini-proteins that contain <50 amino acids often serve as model systems for studying protein folding because their small size makes long timescale simulations possible. However, not all mini-proteins are created equal. The stability and structure of FSD-1, a 28-residue mini-protein that adopted the betabetaalpha zinc-finger motif independent of zinc binding, was investigated using circular dichroism, differential scanning calorimetry, and replica-exchange molecular dynamics. The broad melting transition of FSD-1, similar to that of a helix-to-coil transition, was observed by using circular dichroism, differential scanning calorimetry, and replica-exchange molecular dynamics. The N-terminal beta-hairpin was found to be flexible. The FSD-1 apparent melting temperature of 41 degrees C may be a reflection of the melting of its alpha-helical segment instead of the entire protein. Thus, despite its attractiveness due to small size and purposefully designed helix, sheet, and turn structures, the status of FSD-1 as a model system for studying protein folding should be reconsidered.
authors.affiliation: Center for Computational Biology, Department of Biochemistry and Molecular Biophysics, Washington University in St. Louis, St. Louis, Missouri, USA. jafeng@artsci.wustl.edu
authors.forename: Jianwen A
authors.initials: JA
authors.lastname: Feng
authors.forename: Jeff
authors.initials: J
authors.lastname: Kao
authors.forename: Garland R
authors.initials: GR
authors.lastname: Marshall
mesh_terms: D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D003198:Computer Simulation; D004268:DNA-Binding Proteins / Q000737:chemistry*; D006860:Hydrogen Bonding; D008956:Models, Chemical; D008958:Models, Molecular; D044367:Phase Transition; D017510:Protein Folding; D055550:Protein Stability; D017433:Protein Structure, Secondary; D013696:Temperature; D014157:Transcription Factors / Q000737:chemistry*; D044366:Transition Temperature
chemical_list: D004268:DNA-Binding Proteins; C108466:FSD-1 protein, synthetic; D014157:Transcription Factors