TY  - JOUR
ID  - 13
A1  - Bhasin,N.
A1  - Carl,P.
A1  - Harper,S.
A1  - Gang Feng
A1  - Hui Lu
A1  - Speicher,D. W.
A1  - Discher,D. E.
T1  - Chemistry on a single protein, vascular cell adhesion molecule-1, during forced unfolding
Y1  - 2004
Y2  - Oct 29
VL  - 279
IS  - 44
SP  - 45865
EP  - 45874
KW  - Disulfides/chemistry
KW  - Dithiothreitol/pharmacology
KW  - Humans
KW  - Oxidation-Reduction
KW  - Protein Folding
KW  - Research Support, U.S. Gov't, Non-P.H.S.
KW  - Research Support, U.S. Gov't, P.H.S.
KW  - Vascular Cell Adhesion Molecule-1/chemistry
AB  - Proteins of many types experience tensile forces in their normal function, and vascular cell adhesion molecule-1 (VCAM-1) is typical in this. VCAM has seven Ig domains, and each has a disulfide bond (-S-S-) buried in its core that covalently stabilizes about half of each domain against unfolding. VCAM is extended here by single molecule atomic force microscopy in the presence or absence of reducing agents. In the absence of reducing agent, a sawtooth pattern of forced unfolding reveals an average period and total length consistent with disulfide locations in VCAM. With increasing reducing agent, accessible disulfides are specifically reduced (to SH); the average period for unfolding increases up to saturation together with additional metrics of unfolding. Steered molecular dynamics simulations of unfolding indeed show that the core disulfide bond is solvent-exposed in the very earliest stages of protein extension. Michaelis-Menten kinetics emerge with reduction catalyzed by force (tau(reduction) approximately 10(-4) s). The results establish single molecule reduction, one bond at a time, and show that mechanical forces can play a key role in modulating the redox state of cell adhesion proteins that are invariably stressed in cell adhesion.
N1  - DEP: 20040811; JID: 2985121R; 0 (Disulfides); 0 (Vascular Cell Adhesion Molecule-1); 3483-12-3 (Dithiothreitol); 2004/08/11 [aheadofprint]; ppublish
CY  - United States
A3  - Anonymous
SN  - 0021-9258
AD  - Systems Biology and Polymer Engineering Laboratory, the Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
JF  - Journal of Biological Chemistry
JA  - J.Biol.Chem.
M1  - Journal
ER  -