scholarly journals A Non-Canonical Calmodulin Target Motif Comprising a Polybasic Region and Lipidated Terminal Residue Regulates Localization

2020 ◽  
Vol 21 (8) ◽  
pp. 2751
Author(s):  
Benjamin M. M. Grant ◽  
Masahiro Enomoto ◽  
Mitsuhiko Ikura ◽  
Christopher B. Marshall
Keyword(s):  
Electrostatic Interactions ◽  
Binding Motif ◽  
Hydrophobic Pocket ◽  
Anchor Residue ◽  
Binding Motifs ◽  
Downstream Signaling ◽  
C Terminus ◽  
Ef Hand ◽  
Prenylated Proteins ◽  
Hydrophobic Anchor

Calmodulin (CaM) is a Ca2+-sensor that regulates a wide variety of target proteins, many of which interact through short basic helical motifs bearing two hydrophobic ‘anchor’ residues. CaM comprises two globular lobes, each containing a pair of EF-hand Ca2+-binding motifs that form a Ca2+-induced hydrophobic pocket that binds an anchor residue. A central flexible linker allows CaM to accommodate diverse targets. Several reported CaM interactors lack these anchors but contain Lys/Arg-rich polybasic sequences adjacent to a lipidated N- or C-terminus. Ca2+-CaM binds the myristoylated N-terminus of CAP23/NAP22 with intimate interactions between the lipid and a surface comprised of the hydrophobic pockets of both lobes, while the basic residues make electrostatic interactions with the negatively charged surface of CaM. Ca2+-CaM binds farnesylcysteine, derived from the farnesylated polybasic C-terminus of KRAS4b, with the lipid inserted into the C-terminal lobe hydrophobic pocket. CaM sequestration of the KRAS4b farnesyl moiety disrupts KRAS4b membrane association and downstream signaling. Phosphorylation of basic regions of N-/C-terminal lipidated CaM targets can reduce affinity for both CaM and the membrane. Since both N-terminal myristoylated and C-terminal prenylated proteins use a Singly Lipidated Polybasic Terminus (SLIPT) for CaM binding, we propose these polybasic lipopeptide elements comprise a non-canonical CaM-binding motif.

SAC3B is a target of CML19, the centrin 2 of Arabidopsis thaliana

2020 ◽  
Vol 477 (1) ◽  
pp. 173-189 ◽  
Author(s):  
Marco Pedretti ◽  
Carolina Conter ◽  
Paola Dominici ◽  
Alessandra Astegno
Keyword(s):  
Excision Repair ◽  
Complex Structure ◽  
Binding Motif ◽  
C Terminus ◽  
Repair Protein ◽  
Nucleotide Excision ◽  
Ef Hand ◽  
Molecular Determinants ◽  
Structure In Solution

Arabidopsis centrin 2, also known as calmodulin-like protein 19 (CML19), is a member of the EF-hand superfamily of calcium (Ca2+)-binding proteins. In addition to the notion that CML19 interacts with the nucleotide excision repair protein RAD4, CML19 was suggested to be a component of the transcription export complex 2 (TREX-2) by interacting with SAC3B. However, the molecular determinants of this interaction have remained largely unknown. Herein, we identified a CML19-binding site within the C-terminus of SAC3B and characterized the binding properties of the corresponding 26-residue peptide (SAC3Bp), which exhibits the hydrophobic triad centrin-binding motif in a reversed orientation (I8W4W1). Using a combination of spectroscopic and calorimetric experiments, we shed light on the SAC3Bp–CML19 complex structure in solution. We demonstrated that the peptide interacts not only with Ca2+-saturated CML19, but also with apo-CML19 to form a protein–peptide complex with a 1 : 1 stoichiometry. Both interactions involve hydrophobic and electrostatic contributions and include the burial of Trp residues of SAC3Bp. However, the peptide likely assumes different conformations upon binding to apo-CML19 or Ca2+-CML19. Importantly, the peptide dramatically increases the affinity for Ca2+ of CML19, especially of the C-lobe, suggesting that in vivo the protein would be Ca2+-saturated and bound to SAC3B even at resting Ca2+-levels. Our results, providing direct evidence that Arabidopsis SAC3B is a CML19 target and proposing that CML19 can bind to SAC3B through its C-lobe independent of a Ca2+ stimulus, support a functional role for these proteins in TREX-2 complex and mRNA export.

scholarly journals HSP70-binding motifs function as protein quality control degrons

2021 ◽  
Author(s):  
Amanda B Abildgaard ◽  
Søren D Petersen ◽  
Fia B Larsen ◽  
Caroline Kampmeyer ◽  
Kristoffer E Johansson ◽  
...  
Keyword(s):  
Quality Control ◽  
Protein Quality ◽  
Protein Quality Control ◽  
Ubiquitin Proteasome System ◽  
Misfolded Proteins ◽  
Binding Motif ◽  
Binding Motifs ◽  
C Terminus ◽  
Ubiquitin Proteasome ◽  
Chaperone Binding

Protein quality control (PQC) degrons are short protein segments that target misfolded proteins for degradation through the ubiquitin-proteasome system (UPS). To uncover how PQC degrons function, we performed a screen in Saccharomyces cerevisiae by fusing a library of flexible tetrapeptides to the C-terminus of the Ura3-HA-GFP reporter. The identified degrons exhibited high sequence variation but with marked hydrophobicity. Notably, the best scoring degrons constitute predicted Hsp70-binding motifs. When directly tested, a canonical Hsp70 binding motif (RLLL) functioned as a dose-dependent PQC degron that was targeted by Hsp70, Hsp110, Fes1, several Hsp40 J-domain co-chaperones and the PQC E3 ligase Ubr1. Our results suggest that multiple PQC degrons overlap with chaperone-binding sites and that PQC-linked degradation achieves specificity via chaperone binding. Thus, the PQC system has evolved to exploit the intrinsic capacity of chaperones to recognize misfolded proteins, thereby placing them at the nexus of protein folding and degradation.

scholarly journals Insight into Calcium-Binding Motifs of Intrinsically Disordered Proteins

Biomolecules ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1173
Author(s):  
Estella A. Newcombe ◽  
Catarina B. Fernandes ◽  
Jeppe E. Lundsgaard ◽  
Inna Brakti ◽  
Kresten Lindorff-Larsen ◽  
...  
Keyword(s):  
Calcium Binding ◽  
Intrinsically Disordered Proteins ◽  
Disordered Proteins ◽  
Binding Motif ◽  
Binding Motifs ◽  
Functional Roles ◽  
Intrinsically Disordered ◽  
Ef Hand ◽  
Folded Proteins ◽  
Affinity Quantification

Motifs within proteins help us categorize their functions. Intrinsically disordered proteins (IDPs) are rich in short linear motifs, conferring them many different roles. IDPs are also frequently highly charged and, therefore, likely to interact with ions. Canonical calcium-binding motifs, such as the EF-hand, often rely on the formation of stabilizing flanking helices, which are a key characteristic of folded proteins, but are absent in IDPs. In this study, we probe the existence of a calcium-binding motif relevant to IDPs. Upon screening several carefully selected IDPs using NMR spectroscopy supplemented with affinity quantification by colorimetric assays, we found calcium-binding motifs in IDPs which could be categorized into at least two groups—an Excalibur-like motif, sequentially similar to the EF-hand loop, and a condensed-charge motif carrying repetitive negative charges. The motifs show an affinity for calcium typically in the ~100 μM range relevant to regulatory functions and, while calcium binding to the condensed-charge motif had little effect on the overall compaction of the IDP chain, calcium binding to Excalibur-like motifs resulted in changes in compaction. Thus, calcium binding to IDPs may serve various structural and functional roles that have previously been underreported.

Tyrosine-protein kinase Src regulates Kv1.5 channel activity and membrane expression through interaction with the N-terminus of the channel

2020 ◽  
Author(s):  
Taylore Dodd ◽  
Tingzhong Wang ◽  
Shetuan Zhang
Keyword(s):  
Protein Kinase ◽  
Cell Voltage ◽  
Underlying Mechanism ◽  
Delayed Rectifier ◽  
Binding Motif ◽  
Membrane Expression ◽  
Binding Motifs ◽  
Delayed Rectifier Potassium Current ◽  
N Terminus ◽  
Tyrosine Protein Kinase

Kv1.5 is a voltage-gated potassium channel that generates the ultra-rapid delayed rectifier potassium current (IKur) important in the repolarization of the atrial action potential. Malfunction of the Kv1.5 channel often results in atrial fibrillation (AFib). A reduction in Kv1.5 current (IKv1.5) occurs upon activation of the endogenous tyrosine-protein kinase Src. The Src SH3 domain binds to proline-rich motifs located within the N-terminus of Kv1.5. Disruption of these binding motifs has been involved in the development of familial AFib. The mechanism underlying the reduction of IKv1.5 upon Src activation has not yet been established and the relationship between Kv1.5 and Src is poorly understood. Therefore, the present study aims to further elucidate the mechanism behind IKv1.5  reduction. The hypothesis that Src regulates Kv1.5 activity by altering the density of mature membrane-localized channels was tested using whole-cell voltage clamp and Western blot analysis. We demonstrate that Src tonically inhibits Kv1.5 activity and decreases the density of mature membrane-localized channels. Kv1.5 channels possessing mutations within the Src binding motifs were also investigated and it was determined that each binding motif contributes to the Kv1.5-Src relationship, however, the binding of Src to an individual motif is sufficiently effective. Our findings indicate that Src regulates Kv1.5 through an interaction with the N-terminal binding motifs and suggests that the inhibition of forward trafficking may be involved in the underlying mechanism. (Supported by the Heart and Stroke foundation of Canada and The Canadian Institutes of Health Research).

scholarly journals Prediction of GluN2B-CT1290-1310/DAPK1 Interaction by Protein–Peptide Docking and Molecular Dynamics Simulation

Molecules ◽  
2018 ◽  
Vol 23 (11) ◽  
pp. 3018 ◽  
Author(s):  
Gao Tu ◽  
Tingting Fu ◽  
Fengyuan Yang ◽  
Lixia Yao ◽  
Weiwei Xue ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Free Energy ◽  
Electrostatic Interactions ◽  
Binding Free Energy ◽  
Computational Simulation ◽  
Critical Role ◽  
Dynamics Simulation ◽  
Peptide Docking ◽  
C Terminus ◽  
Free Energy Decomposition

The interaction of death-associated protein kinase 1 (DAPK1) with the 2B subunit (GluN2B) C-terminus of N-methyl-D-aspartate receptor (NMDAR) plays a critical role in the pathophysiology of depression and is considered a potential target for the structure-based discovery of new antidepressants. However, the 3D structures of C-terminus residues 1290–1310 of GluN2B (GluN2B-CT1290-1310) remain elusive and the interaction between GluN2B-CT1290-1310 and DAPK1 is unknown. In this study, the mechanism of interaction between DAPK1 and GluN2B-CT1290-1310 was predicted by computational simulation methods including protein–peptide docking and molecular dynamics (MD) simulation. Based on the equilibrated MD trajectory, the total binding free energy between GluN2B-CT1290-1310 and DAPK1 was computed by the mechanics generalized born surface area (MM/GBSA) approach. The simulation results showed that hydrophobic, van der Waals, and electrostatic interactions are responsible for the binding of GluN2B-CT1290–1310/DAPK1. Moreover, through per-residue free energy decomposition and in silico alanine scanning analysis, hotspot residues between GluN2B-CT1290-1310 and DAPK1 interface were identified. In conclusion, this work predicted the binding mode and quantitatively characterized the protein–peptide interface, which will aid in the discovery of novel drugs targeting the GluN2B-CT1290-1310 and DAPK1 interface.

Molecular cloning and expression of visinin-like protein 1 from Gekko japonicus spinal cord

Biologia ◽  
2010 ◽  
Vol 65 (1) ◽  
Author(s):  
Lijie Ren ◽  
Xiaosong Gu ◽  
Yan Liu ◽  
Fei Ding ◽  
Xingxing Gu ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Rna Binding ◽  
Cloning And Expression ◽  
Rt Pcr ◽  
Binding Motifs ◽  
Reading Frame ◽  
Dsrna Binding ◽  
Gekko Japonicus ◽  
Ef Hand ◽  
The Central Nervous System

AbstractVisinin-like protein 1 (VILIP-1), a myristoylated calcium sensor protein of the EF-hand Ca2+-binding protein superfamily, plays multiple physiological roles in the central nervous system and peripheral organs. In present study, the cDNA encoding VILIP-1 was identified from the brain and spinal cord cDNA library of Gekko japonicus. It contains a 573 bp open reading frame corresponding to a deduced protein of 191 amino acids. Gecko VILIP-1 shares more than 95.3% identity with vertebrate VILIP-1 proteins, and structurally consists of conserved four EF-hand Ca2+-binding motifs and one dsRNA-binding domain, suggesting that selective pressure must have been extremely high for the conservation of VILIP-1 during vertebrate evolution. Northern blot and RT-PCR showed that gecko VILIP-1 was ubiquitously expressed in all tissues examined. In situ hybridization revealed that the VILIP-1 transcript mainly appeared in the gray matter of the spinal cord, with less distribution in the white matter. Semiquantitative RT-PCR also showed that VILIP-1 expression in spinal cord after tail amputation remained stable at 1 day and 1 week, but decreased at 2 weeks, a time coinciding with regeneration bud formation. This suggests that VILIP-1 may function as a regeneration-associated factor in the form of a monomer or/and RNA-binding complex.

scholarly journals MARCKS domain phosphorylation regulates the differential interaction of Diacylglycerol Kinase ζ with Rac1, RhoA and Syntrophin

2020 ◽  
Author(s):  
Ryan Ard ◽  
Jean-Christian Maillet ◽  
Elias Daher ◽  
Michael Phan ◽  
Radoslav Zinoviev ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Molecular Mechanisms ◽  
Rho Gtpase ◽  
Pdz Domain ◽  
Diacylglycerol Kinase ◽  
Binding Motif ◽  
Membrane Blebbing ◽  
Rhoa Activity ◽  
C Terminus ◽  
Mechanistic Basis

AbstractCells can switch between Rac1, lamellipodia-based and RhoA, blebbing-based migration modes but the molecular mechanisms regulating this choice are not fully understood. Diacylglycerol kinase ζ (DGKζ), which phosphorylates diacylglycerol to yield phosphatidic acid, forms independent complexes with Rac1 and RhoA, selectively dissociating each from RhoGDI. DGKζ catalytic activity is required for Rac1 dissociation but is dispensable for RhoA dissociation. Instead, DGKζ functions as a scaffold that stimulates RhoA release by enhancing RhoGDI phosphorylation by protein kinase Cα (PKCα). Here, PKCα-mediated phosphorylation of the DGKζ MARCKS domain increased DGKζ association with RhoA and decreased its interaction with Rac1. The same modification increased binding of the DGKζ C-terminus to the α1-syntrophin PDZ domain. Expression of a phosphomimetic DGKζ mutant stimulated membrane blebbing in mouse embryonic fibroblasts and C2C12 myoblasts, which was augmented by inhibition of endogenous Rac1. DGKζ expression in differentiated C2 myotubes, which have low endogenous Rac1 levels, also induced substantial membrane blebbing via the Rho-ROCK pathway. These events were independent of DGKζ catalytic activity, but dependent upon a functional C-terminal PDZ-binding motif. Rescue of RhoA activity in DGKζ-null cells required the PDZ-binding motif, suggesting syntrophin interaction is necessary for optimal RhoA activation. Collectively, our results define a switch-like mechanism involving DGKζ phosphorylation by PKCα that favours RhoA-driven blebbing over Rac1-driven lamellipodia formation and macropinocytosis. These findings provide a mechanistic basis for the effect of PKCα signaling on Rho GTPase activity and suggest PKCα activity plays a role in the interconversion between Rac1 and RhoA signaling that underlies different migration modes.

scholarly journals ArabidopsisImmunophilin-like TWD1 Functionally Interacts with Vacuolar ABC Transporters

2004 ◽  
Vol 15 (7) ◽  
pp. 3393-3405 ◽  
Author(s):  
Markus Geisler ◽  
Marjolaine Girin ◽  
Sabine Brandt ◽  
Vincent Vincenzetti ◽  
Sonia Plaza ◽  
...  
Keyword(s):  
Protein Interactions ◽  
Abc Transporters ◽  
Loss Of Function ◽  
Protein Protein Interactions ◽  
Binding Motifs ◽  
Calmodulin Binding ◽  
C Terminus ◽  
Domain Mapping ◽  
Tetratricopeptide Repeat Domain

Previously, the immunophilin-like protein TWD1 from Arabidopsis has been demonstrated to interact with the ABC transporters AtPGP1 and its closest homologue, AtPGP19. Physiological and biochemical investigation of pgp1/pgp19 and of twd1 plants suggested a regulatory role of TWD1 on AtPGP1/AtPGP19 transport activities. To further understand the dramatic pleiotropic phenotype that is caused by loss-of-function mutation of the TWD1 gene, we were interested in other TWD1 interacting proteins. AtMRP1, a multidrug resistance-associated (MRP/ABCC)-like ABC transporter, has been isolated in a yeast two-hybrid screen. We demonstrate molecular interaction between TWD1 and ABC transporters AtMRP1 and its closest homologue, AtMRP2. Unlike AtPGP1, AtMRP1 binds to the C-terminal tetratricopeptide repeat domain of TWD1, which is well known to mediate protein-protein interactions. Domain mapping proved that TWD1 binds to a motif of AtMRP1 that resembles calmodulin-binding motifs; and calmodulin binding to the C-terminus of MRP1 was verified. By membrane fractionation and GFP-tagging, we localized AtMRP1 to the central vacuolar membrane and the TWD1-AtMRP1 complex was verified in vivo by coimmunoprecipitation. We were able to demonstrate that TWD1 binds to isolated vacuoles and has a significant impact on the uptake of metolachlor-GS and estradiol-β-glucuronide, well-known substrates of vacuolar transporters AtMRP1 and AtMRP2.

scholarly journals Engineering of Adenovirus Vectors Containing Heterologous Peptide Sequences in the C Terminus of Capsid Protein IX

2002 ◽  
Vol 76 (14) ◽  
pp. 6893-6899 ◽  
Author(s):  
Igor P. Dmitriev ◽  
Elena A. Kashentseva ◽  
David T. Curiel
Keyword(s):  
Heparan Sulfate ◽  
Capsid Protein ◽  
Minor Component ◽  
Cell Types ◽  
Binding Motif ◽  
Flag Epitope ◽  
C Terminus ◽  
Protein Ix ◽  
A Minor ◽  
Carboxy Terminal

ABSTRACT The utility of the present generation of adenovirus (Ad) vectors for gene therapy applications could be improved by restricting native viral tropism to selected cell types. In order to achieve modification of Ad tropism, we proposed to exploit a minor component of viral capsid, protein IX (pIX), for genetic incorporation of targeting ligands. Based on the proposed structure of pIX, we hypothesized that its C terminus could be used as a site for incorporation of heterologous peptide sequences. We engineered recombinant Ad vectors containing modified pIX carrying a carboxy-terminal Flag epitope along with a heparan sulfate binding motif consisting of either eight consecutive lysines or a polylysine sequence. Using an anti-Flag antibody, we have shown that modified pIXs are incorporated into virions and display Flag-containing C-terminal sequences on the capsid surface. In addition, both lysine octapeptide and polylysine ligands were accessible for binding to heparin-coated beads. In contrast to virus bearing lysine octapeptide, Ad vector displaying a polylysine was capable of recognizing cellular heparan sulfate receptors. We have demonstrated that incorporation of a polylysine motif into the pIX ectodomain results in a significant augmentation of Ad fiber knob-independent infection of CAR-deficient cell types. Our data suggest that the pIX ectodomain can serve as an alternative to the fiber knob, penton base, and hexon proteins for incorporation of targeting ligands for the purpose of Ad tropism modification.

scholarly journals Tubulin-Dependent Transport of Connexin-36 Potentiates the Size and Strength of Electrical Synapses

Cells ◽  
2019 ◽  
Vol 8 (10) ◽  
pp. 1146 ◽  
Author(s):  
Brown ◽  
del Corsso ◽  
Zoidl ◽  
Donaldson ◽  
Spray ◽  
...  
Keyword(s):  
Protein Transport ◽  
Mutational Analysis ◽  
Binding Motif ◽  
Dependent Manner ◽  
Electrical Synapses ◽  
Binding Motifs ◽  
Connexin 36 ◽  
Dependent Transport ◽  
Carboxy Terminal

Connexin-36 (Cx36) electrical synapses strengthen transmission in a calcium/calmodulin (CaM)/calmodulin-dependent kinase II (CaMKII)-dependent manner similar to a mechanism whereby the N-methyl-D-aspartate (NMDA) receptor subunit NR2B facilitates chemical transmission. Since NR2B–microtubule interactions recruit receptors to the cell membrane during plasticity, we hypothesized an analogous modality for Cx36. We determined that Cx36 binding to tubulin at the carboxy-terminal domain was distinct from Cx43 and NR2B by binding a motif overlapping with the CaM and CaMKII binding motifs. Dual patch-clamp recordings demonstrated that pharmacological interference of the cytoskeleton and deleting the binding motif at the Cx36 carboxyl-terminal (CT) reversibly abolished Cx36 plasticity. Mechanistic details of trafficking to the gap-junction plaque (GJP) were probed pharmacologically and through mutational analysis, all of which affected GJP size and formation between cell pairs. Lys279, Ile280, and Lys281 positions were particularly critical. This study demonstrates that tubulin-dependent transport of Cx36 potentiates synaptic strength by delivering channels to GJPs, reinforcing the role of protein transport at chemical and electrical synapses to fine-tune communication between neurons.

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