Role of aromatic residues in stabilization of the [Fe4S4] cluster in high-potential iron proteins (HiPIPs): physical characterization and stability studies of Tyr-19 mutants of Chromatium vinosum HiPIP.

The functional role of residue Tyr-19 of Chromatium vinosum HiPIP has been evaluated by site-directed mutagenesis experiments. The stability of the [Fe4S4] cluster prosthetic center is sensitive to side-chain replacements. Polar residues result in significant instability, while nonpolar residues (especially with aromatic side chains) maintain cluster stability. Two-dimensional NMR data of native and mutant HiPIPs are consistent with a model where Tyr-19 serves to preserve the structural rigidity of the polypeptide backbone, thereby maintaining a hydrophobic barrier for exclusion of water from the cluster cavity. Solvent accessibility results in more facile oxidation of the cluster by atmospheric oxygen, with subsequent rapid hydrolysis of the [Fe4S4]3+ core.

Structure and stability of a second molten globule intermediate in the apomyoglobin folding pathway.

Apomyoglobin folding proceeds through a molten globule intermediate (low-salt form; I1) that has been characterized by equilibrium (pH 4) and kinetic (pH 6) folding experiments. Of the eight alpha-helices in myoglobin, three (A, G, and H) are structured in I1, while the rest appear to be unfolded. Here we report on the structure and stability of a second intermediate, the trichloroacetate form of the molten globule intermediate (I2), which is induced either from the acid-unfolded protein or from I1 by > or = 5 mM sodium trichloroacetate. Circular dichroism measurements monitoring urea- and acid-induced unfolding indicate that I2 is more highly structured and more stable than I1. Although I2 exhibits properties closer to those of the native protein, one-dimensional NMR spectra show that it maintains the lack of fixed side-chain structure that is the hallmark of a molten globule. Amide proton exchange and 1H-15N two-dimensional NMR experiments are used to identify the source of the extra helicity observed in I2. The results reveal that the existing A, G, and H helices present in I1 have become more stable in I2 and that a fourth helix--the B helix--has been incorporated into the molten globule. Available evidence is consistent with I2 being an on-pathway intermediate. The data support the view that apomyoglobin folds in a sequential fashion through a single pathway populated by intermediates of increasing structure and stability.

Hydraulics and stability of five Texas inlets /

"January 1981."

Growth and stability of rural economies in the 1980s : differences among counties /

Mode of access: Internet.

Hydraulics and stability of tidal inlets /

Issued August 1977.

Vehicle handling and stability.

Mode of access: Internet.

Calibration and stability characteristics of the Baylor Staff Wave Gage /

"May 1986."

A study of the aerodynamic effects and stability characteristics of buses. Summary report. Volume 1. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

A study of the aerodynamic effects and stability characteristics of buses. Technical report. Volume 2. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

Panel evaluation of the NHTSA approach to the 1960-1963 Corvair handling and stability. Final report.

National Highway Traffic Safety Administration, Washington, D.C.

Procedures for preliminary analysis of tidal inlet hydraulics and stability /

"December 1977."

First-interim report on the hydrodynamics and stability and control of a tandem propeller submarine.

"Contract Nonr-3659(00) (FBM)."

Analysis of salinity structure and stability for Texax estuaries /

"July 1991."

Planets and angels.

Poems.

Planets and people.

Suspended with July 1909.