Structure and function of heme proteins in non-native states: a mini-review.

Structure and function of heme proteins regulated by diverse post-translational modifications.

Rational protein design is a powerful strategy, not only for revealing the structure and function relationship of natural metallo-proteins, but also for creating artificial metalloproteins with improved properties and functions. Myoglobin (Mb), a small heme protein created by nature with diverse functions, has been shown to be an ideal scaffold for rational protein design. The progress reviewed herein includes fine-tuning its native functions of O2 binding and transport, peroxidase activity and nitrite reductase (NIR) activity, and rational expanding its functionalities to peroxygenase, heme-copper oxidase (HCO), nitric oxide reductase (NOR), as well as hydroxylamine reductase. These studies have enhanced our understanding of how metalloproteins work in nature, and provided insights for rational design of functional metalloproteins for practical applications in the future.

Functional tuning and expanding of myoglobin by rational protein design.

Heme post-translational modification plays a key role in tuning the structure and function of heme proteins. We herein report a novel tyrosine-heme covalent C−O bond in an artificially produced sperm whale myoglobin (Mb) mutant, F43Y Mb, which formed spontaneously in vivo between the Tyr43 hydroxy group and the heme 4-vinyl group. This highlights the diverse chemistry of heme post-translational modifications, and lays groundwork for further investigation of the structural and functional diversity of covalently-bound heme proteins.

A novel tyrosine-heme C−O covalent linkage in F43Y myoglobin: a new post-translational modification of heme proteins.

Heme proteins are among the most abundant and important metalloproteins, exerting diverse biological functions including oxygen transport, small molecule sensing, selective C-H bond activation, nitrite reduction, and electron transfer. Rational heme protein designs focus on the modification of the heme-binding active site and the heme group, protein hybridization and domain swapping, and de novo design. These strategies not only provide us with unique advantages for illustrating the structure-property-reactivity-function (SPRF) relationship of heme proteins in nature but also endow us with the ability to create novel biocatalysts and biosensors.

Rational heme protein design: all roads lead to Rome.

Rational design of functional enzymes is a powerful strategy to gain deep insights into more complex native enzymes, such as nitric oxide reductase (NOR). Recently, we engineered a functional model of NOR by creating a two His and one Glu (2-His-1-Glu) non-heme iron center in sperm whale myoglobin (swMb L29E, F43H, H64, called FeBMb(-His)). It was found that FeBMb(-His) adopts a low-spin state with bis-His coordination in the absence of metal ions binding to the designed metal center. However, no structural information was available for the variant in this special spin state. We herein performed molecular modeling of FeBMb(-His) and compared with the X-ray structure of its copper bound derivative, Cu(II)-CN−-FeBMb(-His), resolved recently at a high resolution (1.65 A) (PDB entry 3MN0). The simulated structure shows that mutation of Leu to Glu at position 29 in the hydrophobic heme pocket alters the folding behavior of Mb. The hydrogen bond between Glu29 and His64 further plays a role in stabilizing the bis-His (His64/His93) coordination structure. This study offers an excellent example of using molecular modeling to gain insights in rational design of both structural and functional proteins. Proteins 2011. © 2010 Wiley-Liss, Inc.

Ying-Wu Lin

Papers

Structural insights into a low‐spin myoglobin variant with bis‐histidine coordination from molecular modeling