scholarly journals The S2–S3 Loop of Kv7.4 Channels Is Essential for Calmodulin Regulation of Channel Activation

2021 ◽  
Vol 11 ◽  
Author(s):  
Wenhui Zhuang ◽  
Zhiqiang Yan
Keyword(s):  
Calcium Binding ◽  
Auditory Pathway ◽  
Inhibitory Effect ◽  
Binding Ability ◽  
Double Mutation ◽  
Calcium Dependent ◽  
Kv7 Channels ◽  
Electrophysiological Recordings ◽  
Ef Hands ◽  
Cam Regulation

Kv7.4 (KCNQ4) voltage-gated potassium channels control excitability in the inner ear and the central auditory pathway. Mutations in Kv7.4 channels result in inherited progressive deafness in humans. Calmodulin (CaM) is crucial for regulating Kv7 channels, but how CaM affects Kv7 activity has remained unclear. Here, based on electrophysiological recordings, we report that the third EF hand (EF3) of CaM controls the calcium-dependent regulation of Kv7.4 activation and that the S2–S3 loop of Kv7.4 is essential for the regulation mediated by CaM. Overexpression of the mutant CaM1234, which loses the calcium binding ability of all four EF hands, facilitates Kv7.4 activation by accelerating activation kinetics and shifting the voltage dependence of activation leftwards. The single mutant CaM3, which loses the calcium binding ability of the EF3, phenocopies facilitating effects of CaM1234 on Kv7.4 activation. Kv7.4 channels co-expressed with wild-type (WT) CaM show inhibited activation when intracellular calcium levels increase, while Kv7.4 channels co-expressed with CaM1234 or CaM3 are insensitive to calcium. Mutations C156A, C157A, C158V, R159, and R161A, which are located within the Kv7.4 S2–S3 loop, dramatically facilitate activation of Kv7.4 channels co-expressed with WT CaM but have no effect on activation of Kv7.4 channels co-expressed with CaM3, indicating that these five mutations decrease the inhibitory effect of Ca2+/CaM. The double mutation C156A/R159A decreases Ca2+/CaM binding and completely abolishes CaM-mediated calcium-dependent regulation of Kv7.4 activation. Taken together, our results provide mechanistic insights into CaM regulation of Kv7.4 activation and highlight the crucial role of the Kv7.4 S2–S3 loop in CaM regulation.

scholarly journals Characterization of SCaMC-3-like/slc25a41, a novel calcium-independent mitochondrial ATP-Mg/Pi carrier

2009 ◽  
Vol 418 (1) ◽  
pp. 125-133 ◽  
Author(s):  
Javier Traba ◽  
Jorgina Satrústegui ◽  
Araceli del Arco
Keyword(s):  
Calcium Binding ◽  
Adenine Nucleotide ◽  
Duplication Event ◽  
Intermembrane Space ◽  
Inner Mitochondrial Membrane ◽  
Mitochondrial Carriers ◽  
Calcium Dependent ◽  
Mammalian Genomes ◽  
Ef Hands

The SCaMCs (small calcium-binding mitochondrial carriers) constitute a subfamily of mitochondrial carriers responsible for the ATP-Mg/Pi exchange with at least three paralogues in vertebrates. SCaMC members are proteins with two functional domains, the C-terminal transporter domain and the N-terminal domain which harbours calcium-binding EF-hands and faces the intermembrane space. In the present study, we have characterized a shortened fourth paralogue, SCaMC-3L (SCaMC-3-like; also named slc25a41), which lacks the calcium-binding N-terminal extension. SCaMC-3L orthologues are found exclusively in mammals, showing approx. 60% identity to the C-terminal half of SCaMC-3, its closest paralogue. In mammalian genomes, SCaMC-3 and SCaMC-3L genes are adjacent on the same chromosome, forming a head-to-tail tandem array, and show identical exon–intron boundaries, indicating that SCaMC-3L could have arisen from an SCaMC-3 ancestor by a partial duplication event which occurred prior to mammalian radiation. Expression and functional data suggest that, following the duplication event, SCaMC-3L has acquired more restrictive functions. Unlike the broadly expressed longer SCaMCs, mouse SCaMC-3L shows a limited expression pattern; it is preferentially expressed in testis and, at lower levels, in brain. SCaMC-3L transport activity was studied in yeast deficient in Sal1p, the calcium-dependent mitochondrial ATP-Mg/Pi carrier, co-expressing SCaMC-3L and mitochondrial-targeted luciferase, and it was found to perform ATP-Mg/Pi exchange, in a similar manner to Sal1p or other ATP-Mg/Pi carriers. However, metabolite transport through SCaMC-3L is calcium-independent, representing a novel mechanism involved in adenine nucleotide transport across the inner mitochondrial membrane, different to ADP/ATP translocases or long SCaMC paralogues.

scholarly journals Calmodulin and Calmodulin Binding Proteins in Dictyostelium: A Primer

2020 ◽  
Vol 21 (4) ◽  
pp. 1210
Author(s):  
Danton H. O’Day ◽  
Ryan J. Taylor ◽  
Michael A. Myre
Keyword(s):  
Conformational Changes ◽  
Calcium Binding ◽  
Binding Proteins ◽  
Regulatory Protein ◽  
Model Organism ◽  
Ion Binding ◽  
Calcium Dependent ◽  
Calmodulin Binding ◽  
Human Counterpart ◽  
Ef Hands

Dictyostelium discoideum is gaining increasing attention as a model organism for the study of calcium binding and calmodulin function in basic biological events as well as human diseases. After a short overview of calcium-binding proteins, the structure of Dictyostelium calmodulin and the conformational changes effected by calcium ion binding to its four EF hands are compared to its human counterpart, emphasizing the highly conserved nature of this central regulatory protein. The calcium-dependent and -independent motifs involved in calmodulin binding to target proteins are discussed with examples of the diversity of calmodulin binding proteins that have been studied in this amoebozoan. The methods used to identify and characterize calmodulin binding proteins is covered followed by the ways Dictyostelium is currently being used as a system to study several neurodegenerative diseases and how it could serve as a model for studying calmodulinopathies such as those associated with specific types of heart arrythmia. Because of its rapid developmental cycles, its genetic tractability, and a richly endowed stock center, Dictyostelium is in a position to become a leader in the field of calmodulin research.

Characterization of Arabidopsis calcium-dependent protein kinases: activated or not by calcium?

2012 ◽  
Vol 447 (2) ◽  
pp. 291-299 ◽  
Author(s):  
Marie Boudsocq ◽  
Marie-Jo Droillard ◽  
Leslie Regad ◽  
Christiane Laurière
Keyword(s):  
Protein Kinases ◽  
Calcium Binding ◽  
Molecular Mechanisms ◽  
Calcium Sensitivity ◽  
In Planta ◽  
Calcium Dependent ◽  
Dependent Protein ◽  
Biochemical Level ◽  
Calcium Dependent Protein Kinases ◽  
Ef Hands

CDPKs (calcium-dependent protein kinases), which contain both calmodulin-like calcium binding and serine/threonine protein kinase domains, are only present in plants and some protozoans. Upon activation by a stimulus, they transduce the signal through phosphorylation cascades to induce downstream responses, including transcriptional regulation. To understand the functional specificities of CDPKs, 14 Arabidopsis CPKs (CDPKs in plants) representative of the three main subgroups were characterized at the biochemical level, using HA (haemagglutinin)-tagged CPKs expressed in planta. Most of them were partially or mainly associated with membranes, in agreement with acylation predictions. Importantly, CPKs displayed highly variable calcium-dependences for their kinase activities: seven CPKs from subgroups 1 and 2 were clearly sensitive to calcium with different intensities, whereas six CPKs from subgroup 3 exhibited low or no calcium sensitivity to two generic substrates. Interestingly, this apparent calcium-independence correlated with significant alterations in the predicted EF-hands of these kinases, although they all bound calcium. The noticeable exception, CPK25, was calcium-independent owing to the absence of functional EF-hands. Taken together, the results of the present study suggest that calcium binding differentially affects CDPK isoforms that may be activated by distinct molecular mechanisms.

scholarly journals Molecular Players of EF-hand Containing Calcium Signaling Event in Plants

2019 ◽  
Vol 20 (6) ◽  
pp. 1476 ◽  
Author(s):  
Tapan Mohanta ◽  
Dhananjay Yadav ◽  
Abdul Khan ◽  
Abeer Hashem ◽  
Elsayed Abd_Allah ◽  
...  
Keyword(s):  
Calcium Signaling ◽  
Protein Kinases ◽  
Calcium Binding ◽  
Life Forms ◽  
Terrestrial Environment ◽  
Calcium Dependent ◽  
Ef Hand ◽  
Dependent Protein ◽  
Calcium Dependent Protein Kinases ◽  
Ef Hands

Ca2+ is a universal second messenger that plays a pivotal role in diverse signaling mechanisms in almost all life forms. Since the evolution of life from an aquatic to a terrestrial environment, Ca2+ signaling systems have expanded and diversified enormously. Although there are several Ca2+ sensing molecules found in a cell, EF-hand containing proteins play a principal role in calcium signaling event in plants. The major EF-hand containing proteins are calmodulins (CaMs), calmodulin like proteins (CMLs), calcineurin B-like (CBL) and calcium dependent protein kinases (CDPKs/CPKs). CaMs and CPKs contain calcium binding conserved D-x-D motifs in their EF-hands (one motif in each EF-hand) whereas CMLs contain a D-x3-D motif in the first and second EF-hands that bind the calcium ion. Calcium signaling proteins form a complex interactome network with their target proteins. The CMLs are the most primitive calcium binding proteins. During the course of evolution, CMLs are evolved into CaMs and subsequently the CaMs appear to have merged with protein kinase molecules to give rise to calcium dependent protein kinases with distinct and multiple new functions. Ca2+ signaling molecules have evolved in a lineage specific manner with several of the calcium signaling genes being lost in the monocot lineage.

scholarly journals Fungal Genomes: Suffering with Functional Annotation Errors

2020 ◽  
Author(s):  
Tapan Kumar Mohanta ◽  
Abeer Hashem ◽  
Elsayed Fathi Abd_Allah ◽  
Ahmed AL Harrasi
Keyword(s):  
Calcium Binding ◽  
Functional Annotation ◽  
Sequence Data ◽  
Protein Sequences ◽  
Fungal Species ◽  
Sequencing Data ◽  
Calcium Dependent ◽  
Dependent Protein ◽  
Ef Hands ◽  
Annotation Errors

Abstract Background The genome sequencing data are accumulating at a rapid pace, with the current genome sequence data of more than 5780 species being publicly available at the National Center for Biotechnology Information (NCBI) database alone. However, for the researcher communities to use these data, an error-free functional annotation report is a must. Results Analyses of the whole proteome sequence data of 689 fungal species (7.15 million protein sequences) to find the presence of functional annotation error in several species. Hence, calcium dependent protein kinases (CDPKs) and selenoproteins were targeted for the analysis as it is absent all across the fungi kingdom. The analyses revealed the presence of protein with the functional annotation name CDPK. InterproScan analysis revealed that, none of the protein sequences tagged with name “calcium dependent protein kinase” was found to encode calcium binding EF-hands at the regulatory domain. Similarly, none of a protein sequences with annotation name associated with “selenocysteine” was found to encode Sec (U) amino acid. Conclusion The presence of naming of such functional annotation errors in the fungal kingdom is raised a great concern and need to address it at the earliest possible time.

scholarly journals Proteolysis in Caenorhabditis elegans sex determination: cleavage of TRA-2A by TRA-3

2000 ◽  
Vol 14 (8) ◽  
pp. 901-906
Author(s):  
Sharon B. Sokol ◽  
Patricia E. Kuwabara
Keyword(s):  
Caenorhabditis Elegans ◽  
Membrane Protein ◽  
Cell Fate ◽  
Calcium Binding ◽  
Female Development ◽  
C Elegans ◽  
Calcium Dependent ◽  
Substrate Cleavage ◽  
Ef Hands

The Caenorhabditis elegans tra-3 gene promotes female development in XX hermaphrodites and encodes an atypical calpain regulatory protease lacking calcium-binding EF hands. We report that despite the absence of EF hands, TRA-3 has calcium-dependent proteolytic activity and its proteolytic domain is essential for in vivo function. We show that the membrane protein TRA-2A, which promotes XX female development by repressing the masculinizing protein FEM-3, is a TRA-3 substrate. Cleavage of TRA-2A by TRA-3 generates a peptide predicted to have feminizing activity. These results indicate that proteolysis regulated by calcium may control some aspects of sexual cell fate in C. elegans.

scholarly journals The calcium-dependent ATP-Mg/Pi mitochondrial carrier is a target of glucose-induced calcium signalling in Saccharomyces cerevisiae

2005 ◽  
Vol 392 (3) ◽  
pp. 537-544 ◽  
Author(s):  
Santiago Cavero ◽  
Javier Traba ◽  
Araceli Del Arco ◽  
Jorgina Satrústegui
Keyword(s):  
Calcium Binding ◽  
Mitochondrial Protein ◽  
Calcium Signalling ◽  
Cytosolic Calcium ◽  
Calcium Signal ◽  
Transport Activity ◽  
Wild Type ◽  
Binding Motifs ◽  
Mitochondrial Carrier ◽  
Calcium Dependent

Sal1p is a mitochondrial protein that belongs to the SCaMC (short calcium-binding mitochondrial carrier) subfamily of mitochondrial carriers. The presence of calcium-binding motifs facing the extramitochondrial space allows the regulation of the transport activity of these carriers by cytosolic calcium and provides a new mechanism to transduce calcium signals in mitochondria without the requirement of calcium entry in the organelle. We have studied its transport activity, finding that it is a carboxyatractyloside-resistant ATP-Mg carrier. Mitochondria from a disruption mutant of SAL1 have a 50% reduction in the uptake of ATP. We have also found a clear stimulation of ATP-transport activity by calcium, with an S0.5 of approx. 30 μM. Our results also suggest that Sal1p is a target of the glucose-induced calcium signal which is non-essential in wild-type cells, but becomes essential for transport of ATP into mitochondria in yeast lacking ADP/ATP translocases.

Sign in / Sign up

Export Citation Format

Share Document