title: Single-Molecule Force Spectroscopy Trajectories of a Single Protein and Its Polyproteins Are Equivalent: A Direct Experimental Validation Based on A Small Protein NuG2.
abstract: Single-molecule force spectroscopy (SMFS) has become a powerful tool in investigating the mechanical unfolding/folding of proteins at the single-molecule level. Polyproteins made of tandem identical repeats have been widely used in atomic force microscopy (AFM)-based SMFS studies, where polyproteins not only serve as fingerprints to identify single-molecule stretching events, but may also improve statistics of data collection. However, the inherent assumption of such experiments is that all the domains in the polyprotein are equivalent and one SMFS trajectory of stretching a polyprotein made of n domains is equivalent to n trajectories of stretching a single domain. Such an assumption has not been validated experimentally. Using a small protein NuG2 and its polyprotein (NuG2)4as model systems, here we use optical trapping (OT) to directly validate this assumption. Our results show that OT experiments on NuG2 and (NuG2)4lead to identical parameters describing the unfolding and folding kinetics of NuG2, demonstrating that indeed stretching a polyprotein of NuG2 is equivalent to stretching single NuG2 in force spectroscopy experiments and thus validating the use of polyproteins in SMFS experiments.
authors.affiliation: Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T 1Z1, Canada.|State Key Laboratory of Precision Measurements Technology and Instruments, School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin, 300072, China.
authors.forename: Hai
authors.initials: H
authors.lastname: Lei
authors.affiliation: Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T 1Z1, Canada.|State Key Laboratory of Precision Measurements Technology and Instruments, School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin, 300072, China.
authors.forename: Chengzhi
authors.initials: C
authors.lastname: He
authors.affiliation: State Key Laboratory of Precision Measurements Technology and Instruments, School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin, 300072, China.
authors.forename: Chunguang
authors.initials: C
authors.lastname: Hu
authors.affiliation: Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T 1Z1, Canada.
authors.forename: Jinliang
authors.initials: J
authors.lastname: Li
authors.affiliation: State Key Laboratory of Precision Measurements Technology and Instruments, School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin, 300072, China.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Precision Measurements Technology and Instruments, School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin, 300072, China.
authors.forename: Xiaotang
authors.initials: X
authors.lastname: Hu
authors.affiliation: Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T 1Z1, Canada.|State Key Laboratory of Precision Measurements Technology and Instruments, School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin, 300072, China.
authors.forename: Hongbin
authors.identifier: 0000-0001-7813-1332
authors.initials: H
authors.lastname: Li
mesh_terms: D007700:Kinetics; D017510:Protein Folding; D011506:Proteins / Q000737:chemistry*; D000072760:Single Molecule Imaging / Q000379:methods*
chemical_list: D011506:Proteins
keywords: atomic force microscopy; biophysics; force spectroscopy; optical tweezers; protein folding