@article { ISI:000447471500006,
	title = {Mechanical Unfolding Pathway of the High-Potential Iron-Sulfur Protein Revealed by Single-Molecule Atomic Force Microscopy: Toward a General Unfolding Mechanism for Iron-sulfur Proteins},
	journal = {JOURNAL OF PHYSICAL CHEMISTRY B},
	volume = {122},
	number = {40},
	year = {2018},
	month = {OCT 11},
	pages = {9340-9349},
	abstract = {High-potential iron-sulfur proteins (HiPIPs) are an important class of metalloproteins with a {[}4Fe-4S] cluster coordinated by four cysteine residues. Distinct from other iron-sulfur proteins, the cluster in HiPIP has a high reduction potential, making it an essential electron carrier in bacterial photosynthesis. Here, we combined single-molecule atomic force microscopy and protein engineering techniques to investigate the mechanical unfolding mechanism of HiPIP from Chromatium tepidum (cHiPIP). We found that cHiPIP unfolds in a two-step fashion with the protein sequence sequestered by the iron-sulfur center as a stable unfolding intermediate state. The rupture of the iron-sulfur center of cHiPIP proceeds in two distinct parallel pathways; one pathway involves the concurrent rupture of multiple iron thiolate bonds, and the other one involves the sequential rupture of the iron-thiolate bonds. This mechanistic information was further confirmed by mutational studies. We found that the rupture of the iron-thiolate bonds in reduced and oxidized cHiPIP occurred in the range of 150-180 pN at a pulling speed of 400 nm/s, similar to that measured for iron-thiolate bonds in rubredoxin and ferredoxin. Our results may have important implications for understanding the general unfolding mechanism governing iron-sulfur proteins, as well as the mechanism governing the mechanical rupture of the iron-sulfur center.},
	issn = {1520-6106},
	doi = {10.1021/acs.jpcb.8b07614},
	author = {Li, Jiayu and Li, Hongbin}
}
