scholarly journals Unusual quaternary structure of a homodimeric synergistic-type toxin from mamba snake venom defines its molecular evolution

2020 ◽  
Vol 477 (20) ◽  
pp. 3951-3962
Author(s):  
Narumi Aoki-Shioi ◽  
Chacko Jobichen ◽  
J. Sivaraman ◽  
R. Manjunatha Kini
Keyword(s):  
Disulfide Bond ◽  
Disulfide Bonds ◽  
Quaternary Structure ◽  
Hydrophobic Interactions ◽  
Biological Effects ◽  
Three Dimensional ◽  
Amino Acid Sequences ◽  
Dimensional Structure ◽  
Three Dimensional Structure ◽  
Common Structure

Snake venoms are complex mixtures of enzymes and nonenzymatic proteins that have evolved to immobilize and kill prey animals or deter predators. Among them, three-finger toxins (3FTxs) belong to the largest superfamily of nonenzymatic proteins. They share a common structure of three β-stranded loops extending like fingers from a central core containing all four conserved disulfide bonds. Most 3FTxs are monomers and through subtle changes in their amino acid sequences, they interact with different receptors, ion channels and enzymes to exhibit a wide variety of biological effects. The 3FTxs have further expanded their pharmacological space through covalent or noncovalent dimerization. Synergistic-type toxins (SynTxs) isolated from the deadly mamba venoms, although nontoxic, have been known to enhance the toxicity of other venom proteins. However, the details of three-dimensional structure and molecular mechanism of activity of this unusual class of 3FTxs are unclear. We determined the first three-dimensional structure of a SynTx isolated from Dendroaspis jamesoni jamesoni (Jameson's mamba) venom. The SynTx forms a unique homodimer that is held together by an interchain disulfide bond. The dimeric interface is elaborate and encompasses loops II and III. In addition to the inter-subunit disulfide bond, the hydrogen bonds and hydrophobic interactions between the monomers contribute to the dimer formation. Besides, two sulfate ions that mediate interactions between the monomers. This unique quaternary structure is evolved through noncovalent homodimers such as κ-bungarotoxins. This novel dimerization further enhances the diversity in structure and function of 3FTxs.

PREDICTION OF THE THREE-DIMENSIONAL STRUCTURE OF THE ENZYMATIC PART OF T-PA

1987 ◽  
Author(s):  
A Heckel ◽  
K M Hasselbach
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Active Site ◽  
Serine Proteases ◽  
Three Dimensional ◽  
Amino Acid Sequences ◽  
Dimensional Structure ◽  
Salt Bridges ◽  
Three Dimensional Structure ◽  
Insertions And Deletions

Up to now the three-dimensional structure of t-PA or parts of this enzyme is unknown. Using computer graphical methods the spatial structure of the enzymatic part of t-PA is predicted on the hypothesis, the three-dimensional backbone structure of t-PA being similar to that of other serine proteases. The t-PA model was built up in three steps:1) Alignment of the t-PA sequence with other serine proteases. Comparison of enzyme structures available from Brookhaven Protein Data Bank proved elastase as a basis for modeling.2) Exchange of amino acids of elastase differing from the t-PA sequence. The replacement of amino acids was performed such that backbone atoms overlapp completely and side chains superpose as far as possible.3) Modeling of insertions and deletions. To determine the spatial arrangement of insertions and deletions parts of related enzymes such as chymotrypsin or trypsin were used whenever possible. Otherwise additional amino acid sequences were folded to a B-turn at the surface of the proteine, where all insertions or deletions are located. Finally the side chain torsion angles of amino acids were optimised to prevent close contacts of neigh bouring atoms and to improve hydrogen bonds and salt bridges.The resulting model was used to explain binding of arginine 560 of plasminogen to the active site of t-PA. Arginine 560 interacts with Asp 189, Gly 19 3, Ser 19 5 and Ser 214 of t-PA (chymotrypsin numbering). Furthermore interaction of chromo-genic substrate S 2288 with the active site of t-PA was studied. The need for D-configuration of the hydrophobic amino acid at the N-terminus of this tripeptide derivative could be easily explained.

scholarly journals Analysis of the Thermostability Determinants of Hyperthermophilic Esterase EstE1 Based on Its Predicted Three-Dimensional Structure

2006 ◽  
Vol 72 (4) ◽  
pp. 3021-3025 ◽  
Author(s):  
Jin-Kyu Rhee ◽  
Do-Yun Kim ◽  
Dae-Gyun Ahn ◽  
Jung-Hyuk Yun ◽  
Seung-Hwan Jang ◽  
...  
Keyword(s):  
Homology Modeling ◽  
Hydrophobic Interactions ◽  
3D Structure ◽  
Three Dimensional ◽  
Ion Pair ◽  
Archaeoglobus Fulgidus ◽  
Dimensional Structure ◽  
Three Dimensional Structure ◽  
Structure Relationship

ABSTRACT The three-dimensional (3D) structure of the hyperthermophilic esterase EstE1 was constructed by homology modeling using Archaeoglobus fulgidus esterase as a reference, and the thermostability-structure relationship was analyzed. Our results verified the predicted 3D structure of EstE1 and identified the ion pair networks and hydrophobic interactions that are critical determinants for the thermostability of EstE1.

Characterization of RNase HII substrate recognition using RNase HII–argonaute chimaeric enzymes from Pyrococcus furiosus

2010 ◽  
Vol 426 (3) ◽  
pp. 337-344 ◽  
Author(s):  
Sayaka Kitamura ◽  
Kosuke Fujishima ◽  
Asako Sato ◽  
Daisuke Tsuchiya ◽  
Masaru Tomita ◽  
...  
Keyword(s):  
Amino Acid ◽  
Structural Model ◽  
Pyrococcus Furiosus ◽  
Three Dimensional ◽  
Rnase H ◽  
Amino Acid Sequences ◽  
Dimensional Structure ◽  
Piwi Domain ◽  
Three Dimensional Structure ◽  
Protein Secondary Structures

RNase H (ribonuclease H) is an endonuclease that cleaves the RNA strand of RNA–DNA duplexes. It has been reported that the three-dimensional structure of RNase H is similar to that of the PIWI domain of the Pyrococcus furiosus Ago (argonaute) protein, although the two enzymes share almost no similarity in their amino acid sequences. Eukaryotic Ago proteins are key components of the RNA-induced silencing complex and are involved in microRNA or siRNA (small interfering RNA) recognition. In contrast, prokaryotic Ago proteins show greater affinity for RNA–DNA hybrids than for RNA–RNA hybrids. Interestingly, we found that wild-type Pf-RNase HII (P. furiosus, RNase HII) digests RNA–RNA duplexes in the presence of Mn2+ ions. To characterize the substrate specificity of Pf-RNase HII, we aligned the amino acid sequences of Pf-RNase HII and Pf-Ago, based on their protein secondary structures. We found that one of the conserved secondary structural regions (the fourth β-sheet and the fifth α-helix of Pf-RNase HII) contains family-specific amino acid residues. Using a series of Pf-RNase HII–Pf-Ago chimaeric mutants of the region, we discovered that residues Asp110, Arg113 and Phe114 are responsible for the dsRNA (double-stranded RNA) digestion activity of Pf-RNase HII. On the basis of the reported three-dimensional structure of Ph-RNase HII from Pyrococcus horikoshii, we built a three-dimensional structural model of RNase HII complexed with its substrate, which suggests that these amino acids are located in the region that discriminates DNA from RNA in the non-substrate strand of the duplexes.

Synopses from the poster exhibition organized by I. M. Kerr, 1. Interferon: a tertiary structure predicted from amino acid sequences

1982 ◽  
Vol 299 (1094) ◽  
pp. 125-127 ◽  
Keyword(s):  
Amino Acid ◽  
Amino Acid Sequence ◽  
Tertiary Structure ◽  
Three Dimensional ◽  
Amino Acid Sequences ◽  
Dimensional Structure ◽  
X Ray ◽  
Three Dimensional Structure ◽  
X Ray Crystallography ◽  
Functional Studies

Functional studies on interferon would be helped by a three-dimensional structure for the molecule. However, it may be several years before the structure of the protein is determined by X-ray crystallography. We have therefore used available methods for predicting the secondary - and the tertiary - structure of a protein from its amino acid sequence to propose a tertiary model involving the packing of four a-helices. Details of this work have been published elsewhere (Sternberg & Cohen 1982).

scholarly journals Functional and Early Folding Residues are separated in proteins to increase evolvability and robustness

2018 ◽  
Author(s):  
Sebastian Bittrich ◽  
Michael Schroeder ◽  
Dirk Labudde
Keyword(s):  
Protein Folding ◽  
Hydrophobic Interactions ◽  
Three Dimensional ◽  
Accessible Surface Area ◽  
Topological Descriptors ◽  
Dimensional Structure ◽  
Folding Process ◽  
Three Dimensional Structure ◽  
Starting Point ◽  
Local Conformations

AbstractThe three-dimensional structure of proteins captures evolutionary ancestry, and serves as starting point to understand the origin of diseases. Proteins adopt their structure autonomously by the process of protein folding. Over the last decades, the folding process of several proteins has been studied with temporal and spatial resolution which allowed the identification of so-called Early Folding Residues (EFR) in the folding process. These structurally relevant residues become affected early in the folding process and initiate the formation of secondary structure elements and guide their assembly.Using a dataset of 30 proteins and 3,337 residues provided by the Start2Fold database, discriminative features of EFR were identified by a systematical characterization. Therefore, proteins were represented as graphs in order to analyze topological descriptors of EFR. They constitute crucial connectors of protein regions which are distant at sequence level. Especially, these residues exhibit a high number of non-covalent contacts such as hydrogen bonds and hydrophobic interactions. This tendency also manifest as energetically stable local regions in a knowledge-based potential. Conclusively, these features are not only characteristic for EFR but also differ significantly with respect to functional residues. This unveils a split between structurally and functionally relevant residues in proteins which can drastically improve their evolvability and robustness.The characteristics of EFR cannot be attributed to trivial features such as the accessible surface area. Thus, the presented features are novel descriptors for EFR of the folding process. Potentially, these features can be used to design classifiers to predict EFR from structure or to implement structure quality assessment programs. The shown division of labor between functional and EFR has implications for the prediction of mutation effects as well as protein design and can provide insights into the evolution of proteins. Finally, EFR allow to further the understanding of the protein folding process due to their pivotal role.Author summaryProteins are chains of amino acids which adopt a three-dimensional structure and are then able to catalyze chemical reactions or propagate signals in organisms. Without external influence, most proteins fold into their correct structure, and a small number of Early Folding Residues (EFR) have been shown to become affected at the very start of the process. We demonstrated that these residues are located in energetically stable local conformations. EFR are in contact to many other residues of a protein and act as hubs between sequentially distant regions of a proteins. These distinct characteristics can give insights into what causes certain residues to initiate and guide the folding process. Furthermore, it can help our understanding regarding diseases such as Alzheimer’s or amyotrophic lateral sclerosis which are the result of protein folding gone wrong. We further found that the structurally relevant EFR are almost exclusively non-functional. Proteins separate structure and function, which increases evolvability and robustness and gives guidance for the artificial design of proteins.

scholarly journals Description of the quaternary structure of tetrameric proteins. Forms that show either right-handed or left-handed symmetry at the subunit level

1980 ◽  
Vol 187 (2) ◽  
pp. 297-302 ◽  
Author(s):  
E J Milner-White
Keyword(s):  
Lactate Dehydrogenase ◽  
Quaternary Structure ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Phosphoglycerate Mutase ◽  
High Twist ◽  
Three Dimensional Structure ◽  
Left Handed

A method is described for comparing the shapes of tetrameric proteins whose three-dimensional structure is known. The centres of mass of single subunits are calculated as Cartesian co-ordinates with respect to their three dyad axes. The axes are allocated on the basis of the extent of the intersubunit contacts that they relate. This results in the division of proteins into two classes called right-handed and left-handed. A second division, which also contains right-handed and left-handed forms, is made according to the distances between the centres of mass of the subunits measured across the two axes with the most extensive contacts. Two other parameters have been calculated from the coordinates; they are named “aplanarity” and “twist”. The eight tetramers so far investigated are discussed. One, lactate dehydrogenase, cannot be treated in this way. Among the others, right-handed structures (according to both definitions) are found to be commoner; most have low twist; all are of fairly high aplanarity except phosphoglycerate mutase. Prealbumin is exceptional, being left-handed in both ways and of high twist; it has a figure-of-eight structure with the centres of mass lying in one plane. The changes in the quaternary structure of haemoglobin are also presented by using this approach; on deoxygenation the aplanarity and the twist decrease.

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