title: Elasticity and unfolding of single molecules of the giant muscle protein titin.
abstract: The giant muscle protein titin, also called connectin, is responsible for the elasticity of relaxed striated muscle, as well as acting as the molecular scaffold for thick-filament formation. The titin molecule consists largely of tandem domains of the immunoglobulin and fibronectin-III types, together with specialized binding regions and a putative elastic region, the PEVK domain. We have done mechanical experiments on single molecules of titin to determine their visco-elastic properties, using an optical-tweezers technique. On a fast (0.1s) timescale titin is elastic and force-extension data can be fitted with standard random-coil polymer models, showing that there are two main sources of elasticity: one deriving from the entropy of straightening the molecule; the other consistent with extension of the polypeptide chain in the PEVK region. On a slower timescale and above a certain force threshold, the molecule displays stress-relaxation, which occurs in rapid steps of a few piconewtons, corresponding to yielding of internal structures by about 20 nm. This stress-relaxation probably derives from unfolding of immunoglobulin and fibronectin domains.
authors.affiliation: Muscle Research Group, Department of Veterinary Clinical Science, Bristol University, Langford, UK.
authors.forename: L
authors.initials: L
authors.lastname: Tskhovrebova
authors.forename: J
authors.initials: J
authors.lastname: Trinick
authors.forename: J A
authors.initials: JA
authors.lastname: Sleep
authors.forename: R M
authors.initials: RM
authors.lastname: Simmons
mesh_terms: D064211:Connectin; D004548:Elasticity; D066298:In Vitro Techniques; D008863:Microspheres; D009124:Muscle Proteins / Q000737:chemistry / Q000502:physiology*; D017510:Protein Folding; D011494:Protein Kinases / Q000737:chemistry / Q000502:physiology*
chemical_list: D064211:Connectin; D009124:Muscle Proteins; D011494:Protein Kinases