Sean M. Decatur

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PURPOSE Amyloid fibrils are associated with a variety of human protein misfolding and protein deposition diseases. Previous studies have shown that bovine crystallins form amyloid fibers under denaturing conditions and amyloid fibers accumulate in the lens of mice carrying mutations in crystallin genes. Within differentiating lens fiber cells, crystallins(More)
In order for diatomic ligands to enter and exit myoglobin, there must be substantial displacements of amino acid side chains from their positions in the static X-ray structure. One pathway, involving Arg/Lys45, His64, and Val68, has been studied in greatest detail. In an earlier study (Lambright et al., 1989) we reported the surprising result that mutation(More)
In the sperm whale myoglobin mutant H93G, the proximal histidine is replaced by glycine, leaving a cavity in which exogenous imidazole can bind and ligate the heme iron (Barrick, D. (1994) Biochemistry 33, 6545-6554). Structural studies of this mutant suggest that serine 92 may play an important role in imidazole binding by serving as a hydrogen bond(More)
When nitric oxide (NO) binds to heme proteins, it exerts a repulsive trans effect on the proximal ligand, resulting in weakening or rupture of the proximal ligand-iron bond. The general question of whether NO binding generates a five-coordinate complex with proximal ligand release is important for the function of enzymes such as guanylate cyclase. This(More)
Picosecond mid-IR pump-probe measurements of vibrational relaxation (VR) of CO bound to the active sites of wild-type and mutant myoglobins (Mb) reveal that an approximately linear relationship exists between the protein matrix-induced CO frequency shift and the VR rate. This relation parallels a similar linear relationship seen in a series of heme model(More)
The role of the proximal ligand in determining the structure and ligand binding properties of sperm whale myoglobin has been investigated using the mutant H93G(L), where the proximal histidine has been replaced with glycine, creating a cavity which can be occupied by a variety of exogenous ligands, L, to the iron [Barrick, D. (1994) Biochemistry 33,(More)
A variety of heterocyclic ligands can be exchanged into the proximal cavity of sperm whale myoglobin mutant H93G, providing a simple method for introduction of the equivalent of unnatural amino acid side chains into a functionally critical location in this protein. These modified proteins bind CO on the distal side. 1H NMR data on H93G(Im)CO, where Im is(More)
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