title: Inhibitor binding increases the mechanical stability of staphylococcal nuclease.
abstract: Staphylococcal nuclease (SNase) catalyzes the hydrolysis of DNA and RNA in a calcium-dependent fashion. We used AFM-based single-molecule force spectroscopy to investigate the mechanical stability of SNase alone and in its complex with an SNase inhibitor, deoxythymidine 3',5'-bisphosphate. We found that the enzyme unfolds in an all-or-none fashion at ∼26 pN. Upon binding to the inhibitor, the mechanical unfolding forces of the enzyme-inhibitor complex increase to ∼50 pN. This inhibitor-induced increase in the mechanical stability of the enzyme is consistent with the increased thermodynamical stability of the complex over that of SNase. Because of its strong mechanical response to inhibitor binding, SNase, a model protein folding system, offers a unique opportunity for studying the relationship between enzyme mechanics and catalysis.
authors.affiliation: Graduate Institute of Biotechnology, National Chung-Hsing University, Taichung, Taiwan, Republic of China. [corrected]
authors.forename: Chien-Chung
authors.initials: CC
authors.lastname: Wang
authors.forename: Tian-Yow
authors.initials: TY
authors.lastname: Tsong
authors.forename: Yau-Heiu
authors.initials: YH
authors.lastname: Hsu
authors.forename: Piotr E
authors.initials: PE
authors.lastname: Marszalek
mesh_terms: D001696:Biomechanical Phenomena / Q000187:drug effects; D002118:Calcium / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000378:metabolism* / Q000494:pharmacology*; D004795:Enzyme Stability / Q000187:drug effects; D008836:Micrococcal Nuclease / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D058767:Protein Unfolding / Q000187:drug effects; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013942:Thymine Nucleotides / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D011994:Recombinant Proteins; D013942:Thymine Nucleotides; C019111:thymidine 3',5'-diphosphate; D008836:Micrococcal Nuclease; D002118:Calcium