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Accounts of Chemical Research Apr 2016Metal ions and metallocofactors play important roles in a broad range of biochemical reactions. Accordingly, it has been estimated that as much as 25-50% of the proteome...
Metal ions and metallocofactors play important roles in a broad range of biochemical reactions. Accordingly, it has been estimated that as much as 25-50% of the proteome uses transition metal ions to carry out a variety of essential functions. The metal ions incorporated within metalloproteins fulfill functional roles based on chemical properties, the diversity of which arises as transition metals can adopt different redox states and geometries, dictated by the identity of the metal and the protein environment. The coupling of a metal ion with an organic framework in metallocofactors, such as heme and cobalamin, further expands the chemical functionality of metals in biology. The three-dimensional visualization of metal ions and complex metallocofactors within a protein scaffold is often a starting point for enzymology, highlighting the importance of structural characterization of metalloproteins. Metalloprotein crystallography, however, presents a number of implicit challenges including correctly incorporating the relevant metal or metallocofactor, maintaining the proper environment for the protein to be purified and crystallized (including providing anaerobic, cold, or aphotic environments), and being mindful of the possibility of X-ray induced damage to the proteins or incorporated metal ions. Nevertheless, the incorporated metals or metallocofactors also present unique advantages in metalloprotein crystallography. The significant resonance that metals undergo with X-ray photons at wavelengths used for protein crystallography and the rich electronic properties of metals, which provide intense and spectroscopically unique signatures, allow a metalloprotein crystallographer to use anomalous dispersion to determine phases for structure solution and to use simultaneous or parallel spectroscopic techniques on single crystals. These properties, coupled with the improved brightness of beamlines, the ability to tune the wavelength of the X-ray beam, the availability of advanced detectors, and the incorporation of spectroscopic equipment at a number of synchrotron beamlines, have yielded exciting developments in metalloprotein structure determination. Here we will present results on the advantageous uses of metals in metalloprotein crystallography, including using metallocofactors to obtain phasing information, using K-edge X-ray absorption spectroscopy to identify metals coordinated in metalloprotein crystals, and using UV-vis spectroscopy on crystals to probe the enzymatic activity of the crystallized protein.
Topics: Crystallography, X-Ray; Metalloproteins; Protein Conformation; X-Ray Absorption Spectroscopy
PubMed: 26975689
DOI: 10.1021/acs.accounts.5b00538 -
Cell Jun 2022Zinc (Zn) is an essential micronutrient and cofactor for up to 10% of proteins in living organisms. During Zn limitation, specialized enzymes called metallochaperones...
Zinc (Zn) is an essential micronutrient and cofactor for up to 10% of proteins in living organisms. During Zn limitation, specialized enzymes called metallochaperones are predicted to allocate Zn to specific metalloproteins. This function has been putatively assigned to G3E GTPase COG0523 proteins, yet no Zn metallochaperone has been experimentally identified in any organism. Here, we functionally characterize a family of COG0523 proteins that is conserved across vertebrates. We identify Zn metalloprotease methionine aminopeptidase 1 (METAP1) as a COG0523 client, leading to the redesignation of this group of COG0523 proteins as the Zn-regulated GTPase metalloprotein activator (ZNG1) family. Using biochemical, structural, genetic, and pharmacological approaches across evolutionarily divergent models, including zebrafish and mice, we demonstrate a critical role for ZNG1 proteins in regulating cellular Zn homeostasis. Collectively, these data reveal the existence of a family of Zn metallochaperones and assign ZNG1 an important role for intracellular Zn trafficking.
Topics: Animals; GTP Phosphohydrolases; Homeostasis; Metallochaperones; Metalloendopeptidases; Metalloproteins; Mice; Zebrafish; Zinc
PubMed: 35584702
DOI: 10.1016/j.cell.2022.04.011 -
Current Opinion in Structural Biology Oct 2015Although the structure of enzymes and the chemistry at the catalytic sites have been studied intensively, an understanding of the atomic-scale chemistry requires a new... (Review)
Review
Although the structure of enzymes and the chemistry at the catalytic sites have been studied intensively, an understanding of the atomic-scale chemistry requires a new approach beyond steady state X-ray crystallography and X-ray spectroscopy at cryogenic temperatures. Following the dynamic changes in the geometric and electronic structure of metallo-enzymes at ambient conditions, while overcoming the severe X-ray-induced changes to the redox active catalytic center, is key for deriving reaction mechanisms. Such studies become possible by the intense and ultra-short femtosecond (fs) X-ray pulses from an X-ray free electron laser (XFEL) by acquiring a signal before the sample is destroyed. This review describes the recent and pioneering uses of XFELs to study the protein structure and dynamics of metallo-enzymes using crystallography and scattering, as well as the chemical structure and dynamics of the catalytic complexes (charge, spin, and covalency) using spectroscopy during the reaction to understand the electron-transfer processes and elucidate the mechanism.
Topics: Binding Sites; Crystallography, X-Ray; Lasers; Metalloproteins; Metals; Models, Molecular; Protein Binding; Protein Conformation; Spectrum Analysis; Temperature
PubMed: 26342144
DOI: 10.1016/j.sbi.2015.07.014 -
Angewandte Chemie (International Ed. in... May 2020The relationship between protein structure and function is one of the greatest puzzles within biochemistry. De novo metalloprotein design is a way to wipe the board... (Review)
Review
The relationship between protein structure and function is one of the greatest puzzles within biochemistry. De novo metalloprotein design is a way to wipe the board clean and determine what is required to build in function from the ground up in an unrelated structure. This Review focuses on protein design efforts to create de novo metalloproteins within alpha-helical scaffolds. Examples of successful designs include those with carbonic anhydrase or nitrite reductase activity by incorporating a ZnHis or CuHis site, or that recapitulate the spectroscopic properties of unique electron-transfer sites in cupredoxins (CuHis Cys) or rubredoxins (FeCys ). This work showcases the versatility of alpha helices as scaffolds for metalloprotein design and the progress that is possible through careful rational design. Our studies cover the invariance of carbonic anhydrase activity with different site positions and scaffolds, refinement of our cupredoxin models, and enhancement of nitrite reductase activity up to 1000-fold.
Topics: Drug Design; Electron Transport; Metalloproteins; Protein Conformation, alpha-Helical
PubMed: 31441170
DOI: 10.1002/anie.201907502 -
Chemical Reviews Jul 2022One of the hallmark advances in our understanding of metalloprotein function is showcased in our ability to design new, non-native, catalytically active protein... (Review)
Review
One of the hallmark advances in our understanding of metalloprotein function is showcased in our ability to design new, non-native, catalytically active protein scaffolds. This review highlights progress and milestone achievements in the field of metalloprotein design focused on reports from the past decade with special emphasis on designs couched within common subfields of bioinorganic study: heme binding proteins, monometal- and dimetal-containing catalytic sites, and metal-containing electron transfer sites. Within each subfield, we highlight several of what we have identified as significant and important contributions to either our understanding of that subfield or metalloprotein design as a discipline. These reports are placed in context both historically and scientifically. General suggestions for future directions that we feel will be important to advance our understanding or accelerate discovery are discussed.
Topics: Binding Sites; Catalysis; Catalytic Domain; Electrons; Metalloproteins; Models, Molecular
PubMed: 35763791
DOI: 10.1021/acs.chemrev.1c01025 -
Current Opinion in Structural Biology Dec 2021An estimated half of all proteins contain a metal, with these being essential for a tremendous variety of biological functions. X-ray crystallography is the major method... (Review)
Review
An estimated half of all proteins contain a metal, with these being essential for a tremendous variety of biological functions. X-ray crystallography is the major method for obtaining structures at high resolution of these metalloproteins, but there are considerable challenges to obtain intact structures due to the effects of radiation damage. Serial crystallography offers the prospect of determining low-dose synchrotron or effectively damage free XFEL structures at room temperature and enables time-resolved or dose-resolved approaches. Complementary spectroscopic data can validate redox and or ligand states within metalloprotein crystals. In this opinion, we discuss developments in the application of serial crystallographic approaches to metalloproteins and comment on future directions.
Topics: Catalysis; Crystallography, X-Ray; Metalloproteins; Spectrum Analysis; Synchrotrons
PubMed: 34455163
DOI: 10.1016/j.sbi.2021.07.007 -
Metallomics : Integrated Biometal... May 2014Sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) is commonly used to obtain high resolution separation of complex mixtures of proteins. The method...
Sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) is commonly used to obtain high resolution separation of complex mixtures of proteins. The method initially denatures the proteins that will undergo electrophoresis. Although covalent structural features of resolved proteins can be determined with SDS-PAGE, functional properties are destroyed, including the presence of non-covalently bound metal ions. To address this shortcoming, blue-native (BN)-PAGE has been introduced. This method retains functional properties but at the cost of protein resolving power. To address the need for a high resolution PAGE method that results in the separation of native proteins, experiments tested the impact of changing the conditions of SDS-PAGE on the quality of protein separation and retention of functional properties. Removal of SDS and EDTA from the sample buffer together with omission of a heating step had no effect on the results of PAGE. Reduction of SDS in the running buffer from 0.1% to 0.0375% together with deletion of EDTA also made little impact on the quality of the electrophoretograms of fractions of pig kidney (LLC-PK1) cell proteome in comparison with that achieved with the SDS-PAGE method. The modified conditions were called native (N)SDS-PAGE. Retention of Zn(2+) bound in proteomic samples increased from 26 to 98% upon shifting from standard to modified conditions. Moreover, seven of nine model enzymes, including four Zn(2+) proteins that were subjected to NSDS-PAGE retained activity. All nine were active in BN-PAGE, whereas all underwent denaturation during SDS-PAGE. Metal retention after electrophoresis was additionally confirmed using laser ablation-inductively coupled plasma-mass spectrometry and in-gel Zn-protein staining using the fluorophore TSQ.
Topics: Animals; LLC-PK1 Cells; Mass Spectrometry; Metalloproteins; Metals; Native Polyacrylamide Gel Electrophoresis; Proteome; Swine
PubMed: 24686569
DOI: 10.1039/c4mt00033a -
Angewandte Chemie (International Ed. in... Jan 2012Terpenes are the largest class of small-molecule natural products on earth, and the most abundant by mass. Here, we summarize recent developments in elucidating the... (Review)
Review
Terpenes are the largest class of small-molecule natural products on earth, and the most abundant by mass. Here, we summarize recent developments in elucidating the structure and function of the proteins involved in their biosynthesis. There are six main building blocks or modules (α, β, γ, δ, ε, and ζ) that make up the structures of these enzymes: the αα and αδ head-to-tail trans-prenyl transferases that produce trans-isoprenoid diphosphates from C(5) precursors; the ε head-to-head prenyl transferases that convert these diphosphates into the tri- and tetraterpene precursors of sterols, hopanoids, and carotenoids; the βγ di- and triterpene synthases; the ζ head-to-tail cis-prenyl transferases that produce the cis-isoprenoid diphosphates involved in bacterial cell wall biosynthesis; and finally the α, αβ, and αβγ terpene synthases that produce plant terpenes, with many of these modular enzymes having originated from ancestral α and β domain proteins. We also review progress in determining the structure and function of the two 4Fe-4S reductases involved in formation of the C(5) diphosphates in many bacteria, where again, highly modular structures are found.
Topics: Farnesyl-Diphosphate Farnesyltransferase; Humans; Metalloproteins; Terpenes
PubMed: 22105807
DOI: 10.1002/anie.201103110 -
International Journal of Molecular... Dec 2022Metal chelation can provide structural stability and form reactive centers in metalloproteins. Approximately one third of known protein structures are metalloproteins,... (Review)
Review
Metal chelation can provide structural stability and form reactive centers in metalloproteins. Approximately one third of known protein structures are metalloproteins, and metal binding, or the lack thereof, is often implicated in disease, making it necessary to be able to study these systems in detail. Peptide-metal complexes are both present in nature and can provide a means to focus on the binding region of a protein and control experimental variables to a high degree. Structural studies of peptide complexes with metal ions by nuclear magnetic resonance (NMR) were surveyed for all the essential metal complexes and many non-essential metal complexes. The various methods used to study each metal ion are presented together with examples of recent research. Many of these metal systems have been individually reviewed and this current overview of NMR studies of metallopeptide complexes aims to provide a basis for inspiration from structural studies and methodology applied in the field.
Topics: Coordination Complexes; Magnetic Resonance Spectroscopy; Metals; Peptides; Metalloproteins; Ions
PubMed: 36555599
DOI: 10.3390/ijms232415957 -
Journal of the American Chemical Society Nov 2022Many naturally occurring metalloenzymes are gated by rate-limiting conformational changes, and there exists a critical interplay between macroscopic structural...
Many naturally occurring metalloenzymes are gated by rate-limiting conformational changes, and there exists a critical interplay between macroscopic structural rearrangements of the protein and subatomic changes affecting the electronic structure of embedded metallocofactors. Despite this connection, most artificial metalloproteins (ArMs) are prepared in structurally rigid protein hosts. To better model the natural mechanisms of metalloprotein reactivity, we have developed conformationally switchable ArMs (swArMs) that undergo a large-scale structural rearrangement upon allosteric effector binding. The swArMs reported here contain a Co(dmgH)(X) cofactor (dmgH = dimethylglyoxime and X = N, HC, and Pr). We used UV-vis absorbance and energy-dispersive X-ray fluorescence spectroscopies, along with protein assays, and mass spectrometry to show that these metallocofactors are installed site-specifically and stoichiometrically via direct Co-S cysteine ligation within the glutamine binding protein (GlnBP). Structural characterization by single-crystal X-ray diffraction unveils the precise positioning and microenvironment of the metallocofactor within the protein fold. Fluorescence, circular dichroism, and infrared spectroscopies, along with isothermal titration calorimetry, reveal that allosteric Gln binding drives a large-scale protein conformational change. In swArMs containing a Co(dmgH)(CH) cofactor, we show that the protein stabilizes the otherwise labile Co-S bond relative to the free complex. Kinetics studies performed as a function of temperature and pH reveal that the protein conformational change accelerates this bond dissociation in a pH-dependent fashion. We present swArMs as a robust platform for investigating the interplay between allostery and metallocofactor regulation.
Topics: Metalloproteins; Crystallography, X-Ray; Escherichia coli; Circular Dichroism; Kinetics
PubMed: 36378237
DOI: 10.1021/jacs.2c08885