Zinc (Zn) is one of the most abundant metals and is
essential for life. Through ligand interactions, often with thiolate from
cysteine residues in proteins, Zn can play important structural roles in
organizing protein structure and augmenting protein folding and stability.
However, it is difficult to separate the contributions of Zn-ligand
interactions from those originating from intrinsic protein folding in
experimental studies of Zn-containing metalloproteins, which makes the study of
Zn-ligand interactions in proteins challenging. Here, we used single-molecule
force spectroscopy to directly measure the mechanical rupture force of the
Zn-thiolate bond in Zn-rubredoxin. Our results show that considerable force is
needed to rupture Zn-thiolate bonds (∼170 pN, which is
significantly higher than the force necessary to rupture the coordination bond
between Zn and histidines). To our knowledge, our study not only provides new
information about Zn-thiolate bonds in rubredoxin, it also opens a new avenue
for studying metal-ligand bonds in proteins using single-molecule force
spectroscopy.DOI
Journal: Biophysical Journal
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