title: A thermostable 35-residue subdomain within villin headpiece.
abstract: The actin-bundling protein villin contains, at its extreme C terminus, a compact f-actin binding domain called "headpiece". This 76-amino acid domain from chicken is highly thermostable. Here, we show that the stable folded structure in headpiece is localized to a subdomain formed by the C-terminal 35 residues. The subdomain, denoted HP-35, is monomeric and retains high thermostability, with a Tm of 70( +/- 1) degree C at PH 7.0. There are no cysteine residues in HP-35 and its folding is not dependent on the binding of metals or other ligands. HP-35 is not a molten globule, but instead, has properties expected for a fully folded protein with a unique structure. In particular, the slowly exchanging amide protons in HP-35 have protection factors that are slightly larger than those predicted if exchange occurred only from globally unfolded molecules. NMR studies indicate that the headpiece subdomain contains three short alpha-helices, and that these same helices are present in the corresponding regions of intact headpiece. HP-35 is the smallest monomeric polypeptide characterized consisting of only naturally occurring amino acids that autonomously folds into a unique and thermostable structure without disulfide bonds or ligand binding.
authors.affiliation: Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge 02142, USA.
authors.forename: C J
authors.initials: CJ
authors.lastname: McKnight
authors.forename: D S
authors.initials: DS
authors.lastname: Doering
authors.forename: P T
authors.initials: PT
authors.lastname: Matsudaira
authors.forename: P S
authors.initials: PS
authors.lastname: Kim
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry*; D002645:Chickens; D002942:Circular Dichroism; D019791:Guanidine; D006146:Guanidines; D009682:Magnetic Resonance Spectroscopy; D008840:Microfilament Proteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013696:Temperature; D014357:Trypsin / Q000378:metabolism; D014461:Ultracentrifugation
chemical_list: D002352:Carrier Proteins; D006146:Guanidines; D008840:Microfilament Proteins; D010446:Peptide Fragments; C026615:villin; D014357:Trypsin; D019791:Guanidine