scholarly journals Amyloid Assembly Endows Gad m 1 with Biomineralization Properties

2018 ◽  
Author(s):  
Milagros Castellanos ◽  
Rosa Rodríguez-Pérez ◽  
María Gasset
Keyword(s):  
Calcium Carbonate ◽  
Atlantic Cod ◽  
Fish Muscle ◽  
Binding Motif ◽  
Beta Strand ◽  
Ef Hand ◽  
Acidic Conditions ◽  
Ef Hands ◽  
Amyloid Assembly

Acid proteins capable of nucleating Ca2+ and displaying aggregation capacity play key roles in the formation of calcium carbonate biominerals. EF-hands are among the largest Ca2+-binding motif in proteins. Gad m 1, an Atlantic cod β-parvalbumin isoform, is a monomeric EF-hand protein that acts as a Ca2+ buffer in fish muscle and is able to form amyloids under acidic conditions. Since nucleating Ca2+ protein have a propensity to form extended β-strand structures, we wondered whether amyloid assemblies of a protein containing refolded EF-hand motifs were able to influence the in vitro calcium carbonate crystallization. Here we have used the Gad m 1 chain as model to generate monomeric and amyloid assemblies and analyze their effect on in vitro calcite formation. We found that only amyloid assemblies alter calcite morphology.

Structures and metal-ion-binding properties of the Ca2+-binding helix–loop–helix EF-hand motifs

2007 ◽  
Vol 405 (2) ◽  
pp. 199-221 ◽  
Author(s):  
Jessica L. Gifford ◽  
Michael P. Walsh ◽  
Hans J. Vogel
Keyword(s):  
Metal Ion ◽  
Molten Globule ◽  
Family Members ◽  
Binding Motif ◽  
Metal Ion Binding ◽  
Protein Target ◽  
Helix Loop Helix ◽  
Wide Range ◽  
Ef Hand ◽  
Ef Hands

The ‘EF-hand’ Ca2+-binding motif plays an essential role in eukaryotic cellular signalling, and the proteins containing this motif constitute a large and functionally diverse family. The EF-hand is defined by its helix–loop–helix secondary structure as well as the ligands presented by the loop to bind the Ca2+ ion. The identity of these ligands is semi-conserved in the most common (the ‘canonical’) EF-hand; however, several non-canonical EF-hands exist that bind Ca2+ by a different co-ordination mechanism. EF-hands tend to occur in pairs, which form a discrete domain so that most family members have two, four or six EF-hands. This pairing also enables communication, and many EF-hands display positive co-operativity, thereby minimizing the Ca2+ signal required to reach protein saturation. The conformational effects of Ca2+ binding are varied, function-dependent and, in some cases, minimal, but can lead to the creation of a protein target interaction site or structure formation from a molten-globule apo state. EF-hand proteins exhibit various sensitivities to Ca2+, reflecting the intrinsic binding ability of the EF-hand as well as the degree of co-operativity in Ca2+ binding to paired EF-hands. Two additional factors can influence the ability of an EF-hand to bind Ca2+: selectivity over Mg2+ (a cation with very similar chemical properties to Ca2+ and with a cytoplasmic concentration several orders of magnitude higher) and interaction with a protein target. A structural approach is used in this review to examine the diversity of family members, and a biophysical perspective provides insight into the ability of the EF-hand motif to bind Ca2+ with a wide range of affinities.

scholarly journals The Ca(2+)-binding domains in non-muscle type alpha-actinin: biochemical and genetic analysis.

1993 ◽  
Vol 121 (3) ◽  
pp. 599-606 ◽  
Author(s):  
W Witke ◽  
A Hofmann ◽  
B Köppel ◽  
M Schleicher ◽  
A A Noegel
Keyword(s):  
Biochemical Data ◽  
Actin Binding ◽  
Regulatory Function ◽  
Cross Linking ◽  
Abnormal Phenotype ◽  
Ef Hand ◽  
Ef Hands ◽  
Overlay Assay

Dictyostelium alpha-actinin is a Ca(2+)-regulated F-actin cross-linking protein. To test the inhibitory function of the two EF hands, point mutations were introduced into either one or both Ca(2+)-binding sites. After mutations, the two EF hands were distinguishable with respect to their regulatory activities. Inactivation of EF hand I abolished completely the F-actin cross-linking activity of Dictyostelium discoideum alpha-actinin but Ca2+ binding by EF hand II was still observed in a 45Ca2+ overlay assay. In contrast, after mutation of EF hand II the molecule was still active and inhibited by Ca2+; however, approximately 500-fold more Ca2+ was necessary for inhibition and 45Ca2+ binding could not be detected in the overlay assay. These data indicate that EF hand I has a low affinity for Ca2+ and EF hand II a high affinity, implying a regulatory function of EF hand I in the inhibition of F-actin cross-linking activity. Biochemical data is presented which allows us to distinguish two functions of the EF hand domains in D. discoideum alpha-actinin: (a) at the level of the EF-hands, the Ca(2+)-binding affinity of EF hand I was increased by EF hand II in a cooperative manner, and (b) at the level of the two subunits, the EF hands acted as an on/off switch for actin-binding in the neighboring subunit. To corroborate in vitro observations in an in vivo system we tried to rescue the abnormal phenotype of a mutant (Witke, W., M. Schleicher, A. A. Noegel. 1992. Cell. 68:53-62) by introducing the mutated alpha-actinin cDNAs. In agreement with the biochemical data, only the molecule modified in EF hand II could rescue the abnormal phenotype. Considering the fact that the active construct is "always on" because it requires nonphysiological, high Ca2+ concentrations for inactivation, it is interesting to note that an unregulated alpha-actinin was able to rescue the mutant phenotype.

scholarly journals The Penta-EF-Hand ALG-2 Protein Interacts with the Cytosolic Domain of the SOCE Regulator SARAF and Interferes with Ubiquitination

2020 ◽  
Vol 21 (17) ◽  
pp. 6315
Author(s):  
Wei Zhang ◽  
Ayaka Muramatsu ◽  
Rina Matsuo ◽  
Naoki Teranishi ◽  
Yui Kahara ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Binding Activity ◽  
Negative Regulator ◽  
Hek293 Cells ◽  
Binding Motif ◽  
Protein Database ◽  
Ww Domains ◽  
Ef Hand ◽  
Cytosolic Domain

ALG-2 is a penta-EF-hand Ca2+-binding protein and interacts with a variety of proteins in mammalian cells. In order to find new ALG-2-binding partners, we searched a human protein database and retrieved sequences containing the previously identified ALG-2-binding motif type 2 (ABM-2). After selecting 12 high-scored sequences, we expressed partial or full-length GFP-fused proteins in HEK293 cells and performed a semi-quantitative in vitro binding assay. SARAF, a negative regulator of store-operated Ca2+ entry (SOCE), showed the strongest binding activity. Biochemical analysis of Strep-tagged and GFP-fused SARAF proteins revealed ubiquitination that proceeded during pulldown assays under certain buffer conditions. Overexpression of ALG-2 interfered with ubiquitination of wild-type SARAF but not ubiquitination of the F228S mutant that had impaired ALG-2-binding activity. The SARAF cytosolic domain (CytD) contains two PPXY motifs targeted by the WW domains of NEDD4 family E3 ubiquitin ligases. The PPXY motif proximal to the ABM-2 sequence was found to be more important for both in-cell ubiquitination and post-cell lysis ubiquitination. A ubiquitination-defective mutant of SARAF with Lys-to-Arg substitutions in the CytD showed a slower degradation rate by half-life analysis. ALG-2 promoted Ca2+-dependent CytD-to-CytD interactions of SARAF. The ALG-2 dimer may modulate the stability of SARAF by sterically blocking ubiquitination and by bridging SARAF molecules at the CytDs.

scholarly journals Structural and mechanistic insights into secretagogin-mediated exocytosis

2020 ◽  
Vol 117 (12) ◽  
pp. 6559-6570 ◽  
Author(s):  
Jiao Qin ◽  
Qi Liu ◽  
Zhe Liu ◽  
Yun-Zu Pan ◽  
Luis Sifuentes-Dominguez ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Helical Structure ◽  
Snare Complex ◽  
Dependent Manner ◽  
Ef Hand ◽  
Multiple Cell ◽  
Ef Hands ◽  
Underlying Mechanisms ◽  
Close Homolog

Secretagogin (SCGN) is a hexa–EF-hand protein that is highly expressed in the pancreas, brain, and gastrointestinal tract. SCGN is known to modulate regulated exocytosis in multiple cell lines and tissues; however, its exact functions and underlying mechanisms remain unclear. Here, we report that SCGN interacts with the plasma membrane SNARE SNAP-25, but not the assembled SNARE complex, in a Ca2+-dependent manner. The crystal structure of SCGN in complex with a SNAP-25 fragment reveals that SNAP-25 adopts a helical structure and binds to EF-hands 5 and 6 of SCGN. SCGN strongly inhibits SNARE-mediated vesicle fusion in vitro by binding to SNAP-25. SCGN promotes the plasma membrane localization of SNAP-25, but not Syntaxin-1a, in SCGN-expressing cells. Finally, SCGN controls neuronal growth and brain development in zebrafish, likely via interacting with SNAP-25 or its close homolog, SNAP-23. Our results thus provide insights into the regulation of SNAREs and suggest that aberrant synapse functions underlie multiple neurological disorders caused by SCGN deficiency.

scholarly journals Homology modelling of integrin EF-hands. Evidence for widespread use of a conserved cation-binding site

1992 ◽  
Vol 285 (1) ◽  
pp. 325-331 ◽  
Author(s):  
D S Tuckwell ◽  
A Brass ◽  
M J Humphries
Keyword(s):  
Ligand Binding ◽  
Homology Modelling ◽  
Cation Binding ◽  
Binding Motif ◽  
Binding Model ◽  
Bivalent Cation ◽  
Cation Binding Site ◽  
Ef Hand ◽  
Ef Hands

Integrin alpha-subunits contain three or four peptide sequences that are similar to the EF-hand, a 13-residue bivalent cation-binding motif found in calmodulin and parvalbumin. The integrin sequences differ from classical EF-hands in that they lack a co-ordinating residue at position 12. One hypothesis to explain integrin-ligand binding is that aspartate-containing recognition sequences in integrin ligands, which bind at or near to the EF-hand-like sequences, may take the place of the missing residue and co-ordinate directly to the bound cation. In this report, homology modelling of integrin EF-hand-like sequences has been performed using the X-ray structure of calmodulin as a template in order to assess the functional activity of the integrin sequences. In the calmodulin-integrin hybrid structures, integrin EF-hand-like sequences were able to retain cations whereas control sequences did not. Structural analyses demonstrated that the integrin sequences in the hybrid proteins closely resembled conventional EF-hands. The integrin sequences are therefore highly likely to bind Ca2+ ions in vivo, a prerequisite for the ligand-binding model. Database searching with a matrix derived from known integrin EF-hand-like sequences has been used to identify other proteins containing the integrin EF-hand-like motif. Annexin V (anchorin CII), atrial natriuretic peptide receptors and the 70 kDa heat-shock protein were identified by the matrix; the functions of these proteins are known from previous studies to be bivalent cation-dependent. These findings suggest that the integrin EF-hand-like sequence may be a more common motif than originally thought.

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.

Cytotoxicity Studies of Curcumin Loaded-Cockle Shell-Derived Calcium Carbonate Nanoparticles

2019 ◽  
Vol 09 ◽  
Author(s):  
Maryam Muhammad Mailafiya ◽  
Mohamad Aris Mohd Moklas ◽  
Kabeer Abubakar ◽  
Abubakar Danmaigoro ◽  
Samaila Musa Chiroma ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Safety Margin ◽  
Bone Diseases ◽  
In Vivo Studies ◽  
Normal Cells ◽  
Cytotoxicity Studies ◽  
Standard Techniques ◽  
Cockle Shell

Background: Cockle shell-derived calcium carbonate nanoparticles (CSCaCO3NP) are natural biogenic inorganic material that is used in drug delivery mainly as a bone-remodeling agent as well as a delivery agent for various therapeutics against bone diseases. Curcumin possess wide safety margin and yet puzzled with the problem of poor bioavailability due to insolubility. Propounding in vitro and in vivo studies on toxicity assessments of newly synthesized nanoparticles are ongoing to overcome some crucial challenges regarding their safety administration. Nanotoxicology has paved ways for concise test protocols to monitor sequential events with regards to possible toxicity of newly synthesized nanomaterials. The development of nanoparticle with no or less toxic effect has gained tremendous attentions. Objective: This study aimed at evaluating the in vitro cytotoxic effect of curcumin-loaded cockle shell-derived calcium carbonate nanoparticles (Cur-CSCaCO3NP) and assessing its biocompatibility on normal cells using standard techniques of WST’s assay. Method: Standard techniques of WST’s assay was used for the evaluation of the biocompatibility and cytotoxicity. Result: The result showed that CSCaCO3NP and Cur-CSCaCO3NP possess minimal toxicity and high biocompatibility on normal cells even at higher dose of 500 µg/ml and 40 µg/ml respectively. Conclusion: CSCaCO3NP can be termed an excellent non-toxic nanocarrier for curcumin delivery. Hence, curcumin loaded cockle shell derived calcium carbonate nanoparticles (Cur-CSCaCO3NP) could further be assessed for various in vivo and in vitro therapeutic applications against various bone related ailments.

scholarly journals Calcium Carbonate Nanoparticles—Toxicity and Effect of In Ovo Inoculation on Chicken Embryo Development, Broiler Performance and Bone Status

Animals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 932
Author(s):  
Arkadiusz Matuszewski ◽  
Monika Łukasiewicz ◽  
Jan Niemiec ◽  
Maciej Kamaszewski ◽  
Sławomir Jaworski ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Embryo Development ◽  
Bone Quality ◽  
Chicken Embryo ◽  
Broiler Chickens ◽  
Selection Procedure ◽  
High Specificity ◽  
Control Group ◽  
In Ovo

The use of intensive selection procedure in modern broiler chicken lines has led to the development of several skeletal disorders in broiler chickens. Therefore, current research is focused on methods to improve the bone quality in birds. In ovo technology, using nanoparticles with a high specificity to bones, is a potential approach. The present study aimed to evaluate the effect of in ovo inoculation (IOI) of calcium carbonate nanoparticles (CCN) on chicken embryo development, health status, bone characteristics, and on broiler production results and bone quality. After assessing in vitro cell viability, the IOI procedure was performed with an injection of 500 μg/mL CCN. The control group was not inoculated with CCN. Hatchability, weight, and selected bone and serum parameters were measured in embryos. Part of hatchlings were reared under standard conditions until 42 days, and production results, meat quality, and bone quality of broilers were determined. CCN did not show cytotoxicity to cells and chicken embryo and positively influenced bone parameters of the embryos and of broilers later (calcification) without negatively affecting the production results. Thus, the IOI of CCN could modify the molecular responses at the stage of embryogenesis, resulting in better mineralization, and could provide a sustained effect, thereby improving bone quality in adult birds.

scholarly journals The Highly Conservative Cysteine of Oncomodulin as a Feasible Redox Sensor

Biomolecules ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 66
Author(s):  
Alisa A. Vologzhannikova ◽  
Polina A. Khorn ◽  
Marina P. Shevelyova ◽  
Alexei S. Kazakov ◽  
Victor I. Emelyanenko ◽  
...  
Keyword(s):  
Solvent Accessibility ◽  
Sensory Function ◽  
Hydrophobic Residues ◽  
Metal Free ◽  
Helix Loop Helix ◽  
Redox Sensor ◽  
Ef Hand ◽  
Functional Consequences ◽  
Ef Hands ◽  
Ph Range

Oncomodulin (Ocm), or parvalbumin β, is an 11–12 kDa Ca2+-binding protein found inside and outside of vertebrate cells, which regulates numerous processes via poorly understood mechanisms. Ocm consists of two active Ca2+-specific domains of the EF-hand type (“helix-loop-helix” motif), covered by an EF-hand domain with inactive EF-hand loop, which contains a highly conservative cysteine with unknown function. In this study, we have explored peculiarities of the microenvironment of the conservative Cys18 of recombinant rat Ocm (rWT Ocm), redox properties of this residue, and structural/functional sensitivity of rWT Ocm to the homologous C18S substitution. We have found that pKa of the Cys18 thiol lays beyond the physiological pH range. The measurement of redox dependence of rWT Ocm thiol–disulfide equilibrium (glutathione redox pair) showed that redox potential of Cys18 for the metal-free and Ca2+-loaded protein is of −168 mV and −176 mV, respectively. Therefore, the conservative thiol of rWT Ocm is prone to disulfide dimerization under physiological redox conditions. The C18S substitution drastically reduces α-helices content of the metal-free and Mg2+-bound Ocm, increases solvent accessibility of its hydrophobic residues, eliminates the cooperative thermal transition in the apo-protein, suppresses Ca2+/Mg2+ affinity of the EF site, and accelerates Ca2+ dissociation from Ocm. The distinct structural and functional consequences of the minor structural modification of Cys18 indicate its possible redox sensory function. Since some other EF-hand proteins also contain a conservative redox-sensitive cysteine located in an inactive EF-hand loop, it is reasonable to suggest that in the course of evolution, some of the EF-hands attained redox sensitivity at the expense of the loss of their Ca2+ affinity.

scholarly journals Splicing factor SRSF1 promotes breast cancer progression via oncogenic splice switching of PTPMT1

2021 ◽  
Vol 40 (1) ◽  
Author(s):  
Jun-Xian Du ◽  
Yi-Hong Luo ◽  
Si-Jia Zhang ◽  
Biao Wang ◽  
Cong Chen ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cancer Progression ◽  
High Risk Group ◽  
Clinical Samples ◽  
Binding Motif ◽  
Ki 67 ◽  
Tissue Samples

Abstract Background Intensive evidence has highlighted the effect of aberrant alternative splicing (AS) events on cancer progression when triggered by dysregulation of the SR protein family. Nonetheless, the underlying mechanism in breast cancer (BRCA) remains elusive. Here we sought to explore the molecular function of SRSF1 and identify the key AS events regulated by SRSF1 in BRCA. Methods We conducted a comprehensive analysis of the expression and clinical correlation of SRSF1 in BRCA based on the TCGA dataset, Metabric database and clinical tissue samples. Functional analysis of SRSF1 in BRCA was conducted in vitro and in vivo. SRSF1-mediated AS events and their binding motifs were identified by RNA-seq, RNA immunoprecipitation-PCR (RIP-PCR) and in vivo crosslinking followed by immunoprecipitation (CLIP), which was further validated by the minigene reporter assay. PTPMT1 exon 3 (E3) AS was identified to partially mediate the oncogenic role of SRSF1 by the P-AKT/C-MYC axis. Finally, the expression and clinical significance of these AS events were validated in clinical samples and using the TCGA database. Results SRSF1 expression was consistently upregulated in BRCA samples, positively associated with tumor grade and the Ki-67 index, and correlated with poor prognosis in a hormone receptor-positive (HR+) cohort, which facilitated proliferation, cell migration and inhibited apoptosis in vitro and in vivo. We identified SRSF1-mediated AS events and discovered the SRSF1 binding motif in the regulation of splice switching of PTPMT1. Furthermore, PTPMT1 splice switching was regulated by SRSF1 by binding directly to its motif in E3 which partially mediated the oncogenic role of SRSF1 by the AKT/C-MYC axis. Additionally, PTPMT1 splice switching was validated in tissue samples of BRCA patients and using the TCGA database. The high-risk group, identified by AS of PTPMT1 and expression of SRSF1, possessed poorer prognosis in the stage I/II TCGA BRCA cohort. Conclusions SRSF1 exerts oncogenic roles in BRCA partially by regulating the AS of PTPMT1, which could be a therapeutic target candidate in BRCA and a prognostic factor in HR+ BRCA patient.

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