57 research outputs found
Compensation trends into the 21st century
In this Beyond the Numbers, we review the evolution of private industry health and retirement plans (with a focus on defined contributions and savings and thrift retirement plans) and provide an analysis using recent estimates from the National Compensation Survey (NCS). Where applicable, we refer back to a 1990 article by George Stelluto and Deborah Klein in the Monthly Labor Review in which they discussed historical trends in employee compensation from the 1930s through 1980s and offered information on future expectations for compensation developments
Compensation trends into the 21st century
In this Beyond the Numbers, we review the evolution of private industry health and retirement plans (with a focus on defined contributions and savings and thrift retirement plans) and provide an analysis using recent estimates from the National Compensation Survey (NCS). Where applicable, we refer back to a 1990 article by George Stelluto and Deborah Klein in the Monthly Labor Review in which they discussed historical trends in employee compensation from the 1930s through 1980s and offered information on future expectations for compensation developments
Evolutionary History of a Specialized P450 Propane Monooxygenase
The evolutionary pressures that shaped the specificity and catalytic efficiency of enzymes can only be speculated. While directed evolution experiments show that new functions can be acquired under positive selection with few mutations, the role of negative selection in eliminating undesired activities and achieving high specificity remains unclear. Here we examine intermediates along the ‘lineage’ from a naturally occurring C12–C20 fatty acid hydroxylase (P450BM3) to a laboratory-evolved P450 propane monooxygenase (P450PMO) having 20 heme domain substitutions compared to P450BM3. Biochemical, crystallographic, and computational analyses show that a minimal perturbation of the P450BM3 fold and substrate-binding pocket accompanies a significant broadening of enzyme substrate range and the emergence of propane activity. In contrast, refinement of the enzyme catalytic efficiency for propane oxidation (not, vert, similar 9000-fold increase in kcat/Km) involves profound reshaping and partitioning of the substrate access pathway. Remodeling of the substrate-recognition mechanisms ultimately results in remarkable narrowing of the substrate profile around propane and enables the acquisition of a basal iodomethane dehalogenase activity as yet unknown in natural alkane monooxygenases. A highly destabilizing L188P substitution in a region of the enzyme that undergoes a large conformational change during catalysis plays an important role in adaptation to the gaseous alkane. This work demonstrates that positive selection alone is sufficient to completely respecialize the cytochrome P450 for function on a nonnative substrate
Investigating the effect of available redox protein ratios for the conversion of a steroid by a myxobacterial CYP260A1
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136683/1/feb212619.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136683/2/feb212619_am.pd
Geometric And Electronic Structures Of The His-Fe(Iv)=O And His-Fe(Iv)-Tyr Hemes Of Maug
Biosynthesis of the tryptophan tryptophylquinone (TTQ) cofactor activates the enzyme methylamine dehydrogenase. The diheme enzyme MauG catalyzes O-atom insertion and cross-linking of two Trp residues to complete TTQ synthesis. Solution optical and Mössbauer spectroscopic studies have indicated that the reactive form of MauG during turnover is an unusual bisFe(IV) intermediate, which has been formulated as a His-ligated ferryl heme [Fe(IV)=O] (heme A), and an Fe(IV) heme with an atypical His/Tyr ligation (heme B). In this study, Fe K-edge X-ray absorption spectroscopy and extended X-ray absorption fine structure studies have been combined with density functional theory (DFT) and time-dependent DFT methods to solve the geometric and electronic structures of each heme site in the MauG bisFe(IV) redox state. The ferryl heme site (heme A) is compared with the well-characterized compound I intermediate of cytochrome c peroxidase. Heme B is unprecedented in biology, and is shown to have a six-coordinate, S = 1 environment, with a short (1.85-Å) Fe-O(Tyr) bond. Experimentally calibrated DFT calculations are used to reveal a strong covalent interaction between the Fe and the O(Tyr) ligand of heme B in the high-valence form. A large change in the Fe-O(Tyr) bond distance on going from Fe(II) (2.02 Å) to Fe(III) (1.89 Å) to Fe(IV) (1.85 Å) signifies increasing localization of spin density on the tyrosinate ligand upon sequential oxidation of heme B to Fe(IV). As such, O(Tyr) plays an active role in attaining and stabilizing the MauG bisFe(IV) redox state. © 2012 SBIC
Crystallographic and Single-Crystal Spectral Analysis of the Peroxidase Ferryl Intermediate
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Correction for Chreifi et al., Crystal structure of the pristine peroxidase ferryl center and its relevance to proton-coupled electron transfer
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