The High Resolution Crystal Structure of the Human Tumor Suppressor Maspin Reveals a Novel Conformational Switch in the G-helix

Maspin is a serpin that acts as a tumor suppressor in a range of human cancers, including tumors of the breast and lung. Maspin is crucial for development, because homozygous loss of the gene is lethal; however, the precise physiological role of the molecule is unclear. To gain insight into the function of human maspin, we have determined its crystal structure in two similar, but non-isomorphous crystal forms, to 2.1- and 2.8-Å resolution, respectively. The structure reveals that maspin adopts the native serpin fold in which the reactive center loop is expelled fully from the A β-sheet, makes minimal contacts with the core of the molecule, and exhibits a high degree of flexibility. A buried salt bridge unique to maspin orthologues causes an unusual bulge in the region around the D and E α-helices, an area of the molecule demonstrated in other serpins to be important for cofactor recognition. Strikingly, the structural data reveal that maspin is able to undergo conformational change in and around the G α-helix, switching between an open and a closed form. This change dictates the electrostatic character of a putative cofactor binding surface and highlights this region as a likely determinant of maspin function. The high resolution crystal structure of maspin provides a detailed molecular framework to elucidate the mechanism of function of this important tumor suppressor.

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Structure, interdomain dynamics and pH-dependent autoactivation of pro-rhodesain, the main lysosomal cysteine protease from African trypanosomes

10.1101/2020.11.10.363747 ◽

2020 ◽

Author(s):

Patrick Johé ◽

Elmar Jaenicke ◽

Hannes Neuweiler ◽

Tanja Schirmeister ◽

Christian Kersten ◽

...

Keyword(s):

Crystal Structure ◽

Cysteine Protease ◽

Cathepsin L ◽

Salt Bridge ◽

Correlation Spectroscopy ◽

African Trypanosomes ◽

Lysosomal Cysteine Protease ◽

Control Switch ◽

Α Helix ◽

Dynamics Simulations

AbstractRhodesain is the lysosomal cathepsin L-like cysteine protease of T. brucei rhodesiense, the causative agent of Human African Trypanosomiasis. The enzyme is essential for the proliferation and pathogenicity of the parasite as well as its ability to overcome the blood-brain barrier of the host. Lysosomal cathepsins are expressed as zymogens with an inactivating pro-domain that is cleaved under acidic conditions. A structure of the uncleaved maturation intermediate from a trypanosomal cathepsin L-like protease is currently not available. We thus established the heterologous expression of T. brucei rhodesiense pro-rhodesain in E. coli and determined its crystal structure. The trypanosomal pro-domain differs from non-parasitic pro-cathepsins by a unique, extended α-helix that blocks the active site and whose interactions resemble that of the antiprotozoal inhibitor K11777. Interdomain dynamics between pro- and core protease domain as observed by photoinduced electron transfer fluorescence correlation spectroscopy increase at low pH, where pro-rhodesain also undergoes autocleavage. Using the crystal structure, molecular dynamics simulations and mutagenesis, we identify a conserved interdomain salt bridge that prevents premature intramolecular cleavage at higher pH values and may thus present a control switch for the observed pH-sensitivity of pro-enzyme cleavage in (trypanosomal) CathL-like proteases.

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X-ray structure of a human cardiac muscle troponin C/troponin I chimera in two crystal forms

Acta Crystallographica Section F Structural Biology Communications ◽

10.1107/s2053230x21012395 ◽

2022 ◽

Vol 78 (1) ◽

Author(s):

Chunhong Yan ◽

John S. Sack

Keyword(s):

Crystal Structure ◽

Cardiac Muscle ◽

Troponin I ◽

Troponin C ◽

Switch Region ◽

Crystal Forms ◽

X Ray ◽

Hydrophobic Groove ◽

Parallel Direction ◽

Α Helix

The X-ray crystal structure of a human cardiac muscle troponin C/troponin I chimera has been determined in two different crystal forms and shows a conformation of the complex that differs from that previously observed by NMR. The chimera consists of the N-terminal domain of troponin C (cTnC; residues 1–80) fused to the switch region of troponin I (cTnI; residues 138–162). In both crystal forms, the cTnI residues form a six-turn α-helix that lays across the hydrophobic groove of an adjacent cTnC molecule in the crystal structure. In contrast to previous models, the cTnI helix runs in a parallel direction relative to the cTnC groove and completely blocks the calcium desensitizer binding site of the cTnC–cTnI interface.

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High-Resolution Crystal Structure of Chloroplastic Ribose-5-Phosphate Isomerase from Chlamydomonas reinhardtii—An Enzyme Involved in the Photosynthetic Calvin-Benson Cycle

International Journal of Molecular Sciences ◽

10.3390/ijms21207787 ◽

2020 ◽

Vol 21 (20) ◽

pp. 7787

Author(s):

Théo Le Moigne ◽

Pierre Crozet ◽

Stéphane D. Lemaire ◽

Julien Henri

Keyword(s):

Crystal Structure ◽

High Resolution ◽

Metabolic Pathway ◽

Carbon Fixation ◽

Electron Flow ◽

Structural Data ◽

Post Translational Modifications ◽

Photosynthetic Electron Flow ◽

Biochemical Modeling ◽

Experimental Structure

The Calvin–Benson cycle is the key metabolic pathway of photosynthesis responsible for carbon fixation and relies on eleven conserved enzymes. Ribose-5-phosphate isomerase (RPI) isomerizes ribose-5-phosphate into ribulose-5-phosphate and contributes to the regeneration of the Rubisco substrate. Plant RPI is the target of diverse post-translational modifications including phosphorylation and thiol-based modifications to presumably adjust its activity to the photosynthetic electron flow. Here, we describe the first experimental structure of a photosynthetic RPI at 1.4 Å resolution. Our structure confirms the composition of the catalytic pocket of the enzyme. We describe the homo-dimeric state of the protein that we observed in the crystal and in solution. We also map the positions of previously reported post-translational modifications and propose mechanisms by which they may impact the catalytic parameters. The structural data will inform the biochemical modeling of photosynthesis.

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The crystal structure of PD1, aHaemophilussurface fibril domain

Acta Crystallographica Section F Structural Biology Communications ◽

10.1107/s2053230x17001406 ◽

2017 ◽

Vol 73 (2) ◽

pp. 101-108 ◽

Cited By ~ 2

Author(s):

Jack Wright ◽

Maren Thomsen ◽

Robert Kolodziejczyk ◽

Joshua Ridley ◽

Jessica Sinclair ◽

...

Keyword(s):

Crystal Structure ◽

High Resolution ◽

Electron Micrographs ◽

In Silico ◽

Structural Data ◽

Domain Annotation ◽

Virulent Strains ◽

Trimeric Autotransporter Adhesin ◽

Putative Domain

TheHaemophilussurface fibril (Hsf) is an unusually large trimeric autotransporter adhesin (TAA) expressed by the most virulent strains ofH. influenzae. Hsf is known to mediate adhesion between pathogen and host, allowing the establishment of potentially deadly diseases such as epiglottitis, meningitis and pneumonia. While recent research has suggested that this TAA might adopt a novel `hairpin-like' architecture, the characterization of Hsf has been limited toin silicomodelling and electron micrographs, with no high-resolution structural data available. Here, the crystal structure of Hsf putative domain 1 (PD1) is reported at 3.3 Å resolution. The structure corrects the previous domain annotation by revealing the presence of an unexpected N-terminal TrpRing domain. PD1 represents the first Hsf domain to be solved, and thus paves the way for further research on the `hairpin-like' hypothesis.

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High Resolution Crystal Structure of a Human Tumor Necrosis Factor-α Mutant with Low Systemic Toxicity

Journal of Biological Chemistry ◽

10.1074/jbc.273.4.2153 ◽

1998 ◽

Vol 273 (4) ◽

pp. 2153-2160 ◽

Cited By ~ 28

Author(s):

Sun-Shin Cha ◽

Jeong-Sun Kim ◽

Hyun-Soo Cho ◽

Nam-Kyu Shin ◽

Woojin Jeong ◽

...

Keyword(s):

Crystal Structure ◽

High Resolution ◽

Tumor Necrosis Factor ◽

Tumor Necrosis ◽

Tumor Necrosis Factor Α ◽

Human Tumor ◽

Systemic Toxicity ◽

Human Tumor Necrosis Factor ◽

Factor Α ◽

Necrosis Factor

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High resolution STEM imaging study on high Tc superconductor YBa2CuaO7-x

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100106478 ◽

1988 ◽

Vol 46 ◽

pp. 882-883

Author(s):

H.-J. Ou ◽

J. M. Cowley

Keyword(s):

Crystal Structure ◽

High Resolution ◽

Grain Boundary ◽

Strong Field ◽

Imaging Study ◽

Structure Defects ◽

High Tc ◽

High Tc Superconductor ◽

Diffraction Patterns ◽

Lattice Planes

Using the dedicate VG-HB5 STEM microscope, the crystal structure of high Tc superconductor of YBa2Cu3O7-x has been studied via high resolution STEM (HRSTEM) imaging and nanobeam (∽3A) diffraction patterns. Figure 1(a) and 2(a) illustrate the HRSTEM image taken at 10' times magnification along [001] direction and [100] direction, respectively. In figure 1(a), a grain boundary with strong field contrast is seen between two crystal regions A and B. The grain boundary appears to be parallel to a (110) plane, although it is not possible to determine [100] and [001] axes as it is in other regions which contain twin planes [3]. Following the horizontal lattice lines, from left to right across the grain boundary, a lattice bending of ∽4° is noticed. Three extra lattice planes, indicated by arrows, were found to terminate at the grain boundary and form dislocations. It is believed that due to different chemical composition, such structure defects occur during crystal growth. No bending is observed along the vertical lattice lines.

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Tubulin structure at intermediate resolution

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100140634 ◽

1995 ◽

Vol 53 ◽

pp. 852-853

Author(s):

K. H. Downing ◽

S. G. Wolf ◽

E. Nogales

Keyword(s):

High Resolution ◽

Structural Data ◽

Therapeutic Drug ◽

Zinc Ions ◽

Two Dimensional ◽

X Ray Diffraction ◽

X Ray ◽

Negative Stain ◽

Functional Mechanisms ◽

Tubulin Structure

Microtubules are involved in a host of critical cell activities, many of which involve transport of organelles through the cell. Different sets of microtubules appear to form during the cell cycle for different functions. Knowledge of the structure of tubulin will be necessary in order to understand the various functional mechanisms of microtubule assemble, disassembly, and interaction with other molecules, but tubulin has so far resisted crystallization for x-ray diffraction studies. Fortuitously, in the presence of zinc ions, tubulin also forms two-dimensional, crystalline sheets that are ideally suited for study by electron microscopy. We have refined procedures for forming the sheets and preparing them for EM, and have been able to obtain high-resolution structural data that sheds light on the formation and stabilization of microtubules, and even the interaction with a therapeutic drug.Tubulin sheets had been extensively studied in negative stain, demonstrating that the same protofilament structure was formed in the sheets and microtubules. For high resolution studies, we have found that the sheets embedded in either glucose or tannin diffract to around 3 Å.

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HRTEM study of valleriite, a hydroxide-bearing copper sulfide

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100175442 ◽

1990 ◽

Vol 48 (4) ◽

pp. 462-463

Author(s):

S. Wang ◽

P. R. Buseck

Keyword(s):

Electron Microscope ◽

High Resolution ◽

Copper Sulfide ◽

Carbonaceous Chondrite ◽

Structural Data ◽

Basic Structure ◽

Long Period ◽

Selected Area Electron Diffraction ◽

Transmission Electron ◽

Wavy Structure

Valleriite is an unusual mineral, consisting of intergrowths of sulfide layers (corresponding in structure to the mineral smythite - Fe9S11) and hydroxide layers (corresponding to brucite - Mg(OH2)). It has a composition of approximately 1.526[Mg.68Al.32(OH)2].[Fe1.07Cu.93S2] and consists of two interpenetrating lattices, each of which retains its individual structural and diffraction characteristics parallel to the layering. The valleriite structure is related to that of tochilinite, an unusual iron-rich mineral that is of considerable interest for the origin of certain carbonaceous chondrite meteorites and to those of franckeite and cylindrite, two minerals that are of interest because of their unique morphological and crystallographic properties, e.g., the distinctive curved form of cylindrite and the perfect mica-like cleavage with unusual striations and the long-period wavy structure of franckeite.Our selected-area electron diffraction (SAED) patterns and high-resolution transmission electron microscope (HRTEM) images of valleriite provide new structural data. A basic structure and a new superstructure have been observed.

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