@article {2149,
	title = {Configurational entropy modulates the mechanical stability of protein GB1},
	journal = {Journal of Molecular Biology},
	volume = {379},
	number = {4},
	year = {2008},
	note = {ISI Document Delivery No.: 314NITimes Cited: 10Cited Reference Count: 39Li, Hongbin Wang, Hui-Chuan Cao, Yi Sharma, Deepak Wang, Meijia},
	month = {Jun},
	pages = {871-880},
	type = {Article},
	abstract = {Configurational entropy plays important roles in defining the thermodynamic stability as well as the folding/unfolding kinetics of proteins. Here we combine single-molecule atomic force microscopy and protein engineering techniques to directly examine the role of configurational entropy in the mechanical unfolding kinetics and mechanical stability of proteins. We used a small protein, GB1, as a model system and constructed four mutants that elongate loop 2 of GB1 by 2, 5, 24 and 46 flexible residues, respectively. These loop elongation mutants fold properly as determined by far-UV circular dichroism spectroscopy, suggesting that loop 2 is well tolerant of loop insertions without affecting GB1{\textquoteright}s native structure. Our single-molecule atomic force microscopy results reveal that loop elongation decreases the mechanical stability of GB1 and accelerates the mechanical unfolding kinetics. These results can be explained by the loss of configurational entropy upon closing an unstructured flexible loop using classical polymer theory, highlighting the important role of loop regions in the mechanical unfolding of proteins. This study not only demonstrates a general approach to investigating the structural deformation of the loop regions in mechanical unfolding transition state, but also provides the foundation to use configurational entropy as an effective means to modulate the mechanical stability of proteins, which is of critical importance towards engineering artificial elastomeric proteins with tailored nanomechanical properties. (C) 2008 Elsevier Ltd. All rights reserved.},
	keywords = {configurational entropy, DISULFIDE BONDS, FORCE, FORCE SPECTROSCOPY, FRAGMENT RECONSTITUTION, IMMUNOGLOBULIN BINDING DOMAIN, length, LOOP, MECHANICAL STABILITY, mechanical unfolding, MODULES, resistance, single molecule atomic force microscopy, SINGLE PROTEIN, SPECTROSCOPY, TITIN, TRANSITION-STATE},
	isbn = {0022-2836},
	url = {<Go to ISI>://000256815700018},
	author = {Li, H. B. and Wang, H. C. and Cao, Y. and Sharma, D. and Wang, M.}
}
@article {2035,
	title = {Protein-protein interaction regulates proteins{\textquoteright} mechanical stability},
	journal = {Journal of Molecular Biology},
	volume = {378},
	number = {5},
	year = {2008},
	note = {ISI Document Delivery No.: 305IOTimes Cited: 10Cited Reference Count: 38Cao, Yi Yoo, Teri Zhuang, Shulin Li, Hongbin},
	month = {May},
	pages = {1132-1141},
	type = {Article},
	abstract = {Elastomeric proteins are molecular springs found not only in a variety of biological machines and tissues, but also in biomaterials of superb mechanical properties. Regulating the mechanical stability of elastomeric proteins is not only important for a range of biological processes, but also critical for the use of engineered elastomeric proteins as building blocks to construct nanomechanical devices and novel materials of well-defined mechanical properties. Here we demonstrate that protein-protein interactions can potentially serve as an effective means to regulate the mechanical properties of elastomeric proteins. We show that the binding of fragments of IgG antibody to a small protein, GB1, can significantly enhance the mechanical stability of GB1. The regulation of the mechanical stability of GB1 by IgG fragments is not through direct modification of the interactions in the mechanically key region of GB1; instead, it is accomplished via the long-range coupling between the IgG binding site and the mechanically key region of GB1. Although Fc and Fab bind GB1 at different regions of GB1, their binding to GB1 can increase the mechanical stability of GB1 significantly. Using alanine point mutants of GB1, we show that the amplitude of mechanical stability enhancement of GB1 by Fc does not correlate with the binding affinity, suggesting that binding affinity only affects the population of GB1/human Fc (hFc) complex at a given concentration of hFc, but does not affect the intrinsic mechanical stability of the GB1/hFc complex. Furthermore, our results indicate that the mechanical stability enhancement by IgG fragments is robust and can tolerate sequence/structural perturbation to GB1. Our results demonstrate that the protein-protein interaction is an efficient approach to regulate the mechanical stability of GB1-like proteins and we anticipate that this new methodology will help to develop novel elastomeric proteins with tunable mechanical stability and compliance. (C) 2008 Elsevier Ltd. All rights reserved.},
	keywords = {BINDING, BIOLOGICAL ROLES, CRYSTAL-STRUCTURE, DIHYDROFOLATE-REDUCTASE, DOMAIN, ENGINEERING PROTEINS, FORCE SPECTROSCOPY, FRAGMENT, HUMAN-IGG, MECHANICAL STABILITY, mechanical unfolding, MOLECULAR ELASTICITY, protein-protein interaction, single molecule atomic force microscopy, STABILIZATION},
	isbn = {0022-2836},
	url = {<Go to ISI>://000256171900015},
	author = {Cao, Y. and Yoo, T. and Zhuang, S. L. and Li, H. B.}
}
