scholarly journals Ricardo Miledi. 15 September 1927—18 December 2017

2021 ◽  
Vol 71 ◽  
pp. 423-450
Author(s):  
Ian Parker ◽  
Clarke Slater ◽  
Stuart Cull-Candy ◽  
Angela Vincent
Keyword(s):  
Ion Channels ◽  
Messenger Rna ◽  
Noise Analysis ◽  
Functional Characterization ◽  
Medical Doctor ◽  
Presynaptic Nerve Terminal ◽  
Single Receptor ◽  
University College London ◽  
The Individual ◽  
Patients With Epilepsy

For nearly five decades, Ricardo Miledi was among the foremost researchers in elucidating how nerves transmit signals across synapses. Born in Chihuahua, Mexico, he qualified as a medical doctor, obtained a PhD with Arturo Rosenblueth and then, while in Canberra with John Eccles FRS, was invited by Bernard Katz FRS to join the Biophysics department at University College London, where he stayed from 1958 to 1984. Both independently and with Katz, he demonstrated that influx of calcium into the presynaptic nerve terminal is the essential trigger for the release of the neurotransmitter that carries signals across to the postsynaptic cell. He found that cutting the nerve to a frog's muscle increased the number and distribution of its muscle acetylcholine (ACh) receptors, which he purified and established as membrane proteins. Together with Katz, he introduced the technique of membrane noise analysis to determine the properties of the individual ion channels opened by ACh, providing the first functional characterization of a single receptor with integral ion channel. With Eric Barnard (FRS 1981), he pioneered a new approach facilitating the study of neurotransmitter receptors and ion channels by ‘transplanting’ them from brain and other tissues into large Xenopus oocyte cells by injection of messenger RNA. After moving to the University of California, Irvine, in 1984, he helped to establish the Mexican Institute for Neurobiology at Querétaro. Working in Irvine and Mexico he extended this oocyte expression technique to incorporate transplanted brain membranes, particularly from patients with epilepsy or other neurological disorders. He received many honours for his work, including the Royal Medal (1998), but was happiest working in his lab applying his extraordinary technical skills and imagination to study synaptic transmission and inspiring a generation of neuroscientists.

scholarly journals Identification and Functional Characterization of the p66/p68 Components of the MeCP1 Complex

2002 ◽  
Vol 22 (2) ◽  
pp. 536-546 ◽  
Author(s):  
Qin Feng ◽  
Ru Cao ◽  
Li Xia ◽  
Hediye Erdjument-Bromage ◽  
Paul Tempst ◽  
...  
Keyword(s):  
Functional Characterization ◽  
Cpg Dinucleotides ◽  
Methylated Dna ◽  
Major Mechanism ◽  
Preferential Binding ◽  
Dna Silencing ◽  
The Individual ◽  
Identification And Characterization ◽  
Eukaryotic Genomes

ABSTRACT Methylation of cytosine at CpG dinucleotides is a common feature of many higher eukaryotic genomes. A major biological consequence of DNA methylation is gene silencing. Increasing evidence indicates that recruitment of histone deacetylase complexes by methyl-CpG-binding proteins is a major mechanism of methylated DNA silencing. We have previously reported that the MeCP1 protein complex represses transcription through preferential binding, remodeling, and deacetylation of methylated nucleosomes. To understand the molecular mechanism of the functioning of the MeCP1 complex, the individual components of the MeCP1 complex need to be characterized. In this paper, we report the identification and functional characterization of the p66 and p68 components of the MeCP1 complex. We provide evidence that the two components are different forms of the same zinc finger-containing protein. Analysis of the p66 homologs from different organisms revealed two highly conserved regions, CR1 and CR2. While CR1 is involved in the association of p66 with other MeCP1 components, CR2 plays an important role in targeting p66 and MBD3 to specific loci. Thus, our study not only completes the identification of the MeCP1 components but also reveals the potential function of p66 in MeCP1 complex targeting. The identification and characterization of all the MeCP1 components set the stage for reconstitution of the MeCP1 complex.

Structural and functional analysis of the C-terminal region of Streptococcus gordonii SspB

2021 ◽  
Vol 77 (9) ◽  
pp. 1206-1215
Author(s):  
Norbert Schormann ◽  
Sangeetha Purushotham ◽  
Joshua L. Mieher ◽  
Manisha Patel ◽  
Hui Wu ◽  
...  
Keyword(s):  
Functional Characterization ◽  
Scavenger Receptor ◽  
Protein Docking ◽  
Terminal Region ◽  
Tooth Surface ◽  
Functional Difference ◽  
Streptococcus Gordonii ◽  
Viridans Streptococci ◽  
The Individual ◽  
Terminal Domains

Streptococcus gordonii is a member of the viridans streptococci and is an early colonizer of the tooth surface. Adherence to the tooth surface is enabled by proteins present on the S. gordonii cell surface, among which SspB belongs to one of the most well studied cell-wall-anchored adhesin families: the antigen I/II (AgI/II) family. The C-terminal region of SspB consists of three tandemly connected individual domains that display the DEv-IgG fold. These C-terminal domains contain a conserved Ca2+-binding site and isopeptide bonds, and they adhere to glycoprotein 340 (Gp340; also known as salivary agglutinin, SAG). Here, the structural and functional characterization of the C123 SspB domain at 2.7 Å resolution is reported. Although the individual C-terminal domains of Streptococcus mutans AgI/II and S. gordonii SspB show a high degree of both sequence and structural homology, superposition of these structures highlights substantial differences in their electrostatic surface plots, and this can be attributed to the relative orientation of the individual domains (C1, C2 and C3) with respect to each other and could reflect their specificity in binding to extracellular matrix molecules. Studies further confirmed that affinity for Gp340 or its scavenger receptor cysteine-rich (SRCR) domains requires two of the three domains of C123 SspB, namely C12 or C23, which is different from AgI/II. Using protein–protein docking studies, models for this observed functional difference between C123 SspB and C123 AgI/II in their binding to SRCR1 are presented.

scholarly journals TOK Homologue in Neurospora crassa: First Cloning and Functional Characterization of an Ion Channel in a Filamentous Fungus

2003 ◽  
Vol 2 (1) ◽  
pp. 181-190 ◽  
Author(s):  
Stephen K. Roberts
Keyword(s):  
Ion Channels ◽  
Ion Channel ◽  
Neurospora Crassa ◽  
Filamentous Fungus ◽  
Single Channel ◽  
Functional Characterization ◽  
Reversal Potential ◽  
Channel Activity ◽  
Biophysical Properties ◽  
Patch Clamp Technique

ABSTRACT In contrast to animal and plant cells, very little is known of ion channel function in fungal physiology. The life cycle of most fungi depends on the “filamentous” polarized growth of hyphal cells; however, no ion channels have been cloned from filamentous fungi and comparatively few preliminary recordings of ion channel activity have been made. In an attempt to gain an insight into the role of ion channels in fungal hyphal physiology, a homolog of the yeast K+ channel (ScTOK1) was cloned from the filamentous fungus, Neurospora crassa. The patch clamp technique was used to investigate the biophysical properties of the N. crassa K+ channel (NcTOKA) after heterologous expression of NcTOKA in yeast. NcTOKA mediated mainly time-dependent outward whole-cell currents, and the reversal potential of these currents indicated that it conducted K+ efflux. NcTOKA channel gating was sensitive to extracellular K+ such that channel activation was dependent on the reversal potential for K+. However, expression of NcTOKA was able to overcome the K+ auxotrophy of a yeast mutant missing the K+ uptake transporters TRK1 and TRK2, suggesting that NcTOKA also mediated K+ influx. Consistent with this, close inspection of NcTOKA-mediated currents revealed small inward K+ currents at potentials negative of EK. NcTOKA single-channel activity was characterized by rapid flickering between the open and closed states with a unitary conductance of 16 pS. NcTOKA was effectively blocked by extracellular Ca2+, verapamil, quinine, and TEA+ but was insensitive to Cs+, 4-aminopyridine, and glibenclamide. The physiological significance of NcTOKA is discussed in the context of its biophysical properties.

scholarly journals The patient with epilepsy and medicolegal aspects: a view for the neurologist

2019 ◽  
Vol 77 (10) ◽  
pp. 741-745
Author(s):  
Amur FERREIRA NETO SEGUNDO ◽  
Maren de Moraes e SILVA ◽  
Pilar Bueno Siqueira MERCER ◽  
Carolina REINERT ◽  
Emerson Faria BORGES ◽  
...  
Keyword(s):  
Interpersonal Relationships ◽  
Epileptic Seizures ◽  
Federal Law ◽  
Employment Agreement ◽  
Antiepileptic Medication ◽  
Driver's License ◽  
The Individual ◽  
License Renewal ◽  
Attending Physician ◽  
Patients With Epilepsy

ABSTRACT Patients with epilepsy face innumerable obstacles in daily life, related to work, permission to drive and interpersonal relationships, which require medical guidance. This paper reports a literature review based on scientific articles and civil and traffic system, as a way to resolve doubts about medical obligations in the patient’s permission to drive and work. An employment agreement requires the contractor to guarantee safety conditions as well as requiring the patient, at the pre-employment medical examination, to let the physician know previous medical conditions, including epilepsy. More than 90% of patients with epilepsy omit this information during the application assessment, thus being subject to imputation of ideological falsehood crime as disposied on article 299 of Brazilian Penal Code. Medical confidentiality breaches may only occur in specific situations. In Brazil, the authorization and driver’s license renewal is governed by the Brazilian Traffic Code (Federal Law n° 9503/1997). For patient evaluations, two groups are considered: those on antiepileptic medication and those on medication withdrawal. A favorable report from the attending physician is also required, in both categories. Seizures that occur exclusively during sleep, and focal aware events or prolonged aura are not differentiated from other seizure types disposed in the traffic law. It is the responsibility of the attending physician to analyze each patient individually to resolve conflicts between public safety and the individual patient’s independence. A frank and honest doctor-patient relationship is essential for the patient to understand the public and individual consequences of epileptic seizures and to feel comfortable seeking medical help.

scholarly journals Selected Ionotropic Receptors and Voltage-Gated Ion Channels: More Functional Competence for Human Induced Pluripotent Stem Cell (iPSC)-Derived Nociceptors

2020 ◽  
Vol 10 (6) ◽  
pp. 344 ◽  
Author(s):  
Clemens L. Schoepf ◽  
Maximilian Zeidler ◽  
Lisa Spiecker ◽  
Georg Kern ◽  
Judith Lechner ◽  
...  
Keyword(s):  
Ion Channels ◽  
Functional Characterization ◽  
Scientific Progress ◽  
Model Systems ◽  
Patient Specific ◽  
Preclinical Research ◽  
Specific Research ◽  
Voltage Gated ◽  
Trpv1 Channels ◽  
Induced Pluripotent

Preclinical research using different rodent model systems has largely contributed to the scientific progress in the pain field, however, it suffers from interspecies differences, limited access to human models, and ethical concerns. Human induced pluripotent stem cells (iPSCs) offer major advantages over animal models, i.e., they retain the genome of the donor (patient), and thus allow donor-specific and cell-type specific research. Consequently, human iPSC-derived nociceptors (iDNs) offer intriguingly new possibilities for patient-specific, animal-free research. In the present study, we characterized iDNs based on the expression of well described nociceptive markers and ion channels, and we conducted a side-by-side comparison of iDNs with mouse sensory neurons. Specifically, immunofluorescence (IF) analyses with selected markers including early somatosensory transcription factors (BRN3A/ISL1/RUNX1), the low-affinity nerve growth factor receptor (p75), hyperpolarization-activated cyclic nucleotide-gated channels (HCN), as well as high voltage-gated calcium channels (VGCC) of the CaV2 type, calcium permeable TRPV1 channels, and ionotropic GABAA receptors, were used to address the characteristics of the iDN phenotype. We further combined IF analyses with microfluorimetric Ca2+ measurements to address the functionality of these ion channels in iDNs. Thus, we provide a detailed morphological and functional characterization of iDNs, thereby, underpinning their enormous potential as an animal-free alternative for human specific research in the pain field for unveiling pathophysiological mechanisms and for unbiased, disease-specific personalized drug development.

scholarly journals Pervasive functional translation of noncanonical human open reading frames

Science ◽  
2020 ◽  
Vol 367 (6482) ◽  
pp. 1140-1146 ◽  
Author(s):  
Jin Chen ◽  
Andreas-David Brunner ◽  
J. Zachery Cogan ◽  
James K. Nuñez ◽  
Alexander P. Fields ◽  
...  
Keyword(s):  
Messenger Rna ◽  
Functional Characterization ◽  
Human Leukocyte ◽  
Specific Protein ◽  
Screening Strategy ◽  
Ribosome Profiling ◽  
Open Reading Frames ◽  
Cellular Growth ◽  
Antigen System ◽  
Reading Frames

Ribosome profiling has revealed pervasive but largely uncharacterized translation outside of canonical coding sequences (CDSs). In this work, we exploit a systematic CRISPR-based screening strategy to identify hundreds of noncanonical CDSs that are essential for cellular growth and whose disruption elicits specific, robust transcriptomic and phenotypic changes in human cells. Functional characterization of the encoded microproteins reveals distinct cellular localizations, specific protein binding partners, and hundreds of microproteins that are presented by the human leukocyte antigen system. We find multiple microproteins encoded in upstream open reading frames, which form stable complexes with the main, canonical protein encoded on the same messenger RNA, thereby revealing the use of functional bicistronic operons in mammals. Together, our results point to a family of functional human microproteins that play critical and diverse cellular roles.

Functional characterization of the early steps of tetrapyrrole biosynthesis and modification in Desulfovibrio vulgaris Hildenborough

2009 ◽  
Vol 420 (2) ◽  
pp. 317-326 ◽  
Author(s):  
Susana A. L. Lobo ◽  
Amanda Brindley ◽  
Martin J. Warren ◽  
Lígia M. Saraiva
Keyword(s):  
Functional Characterization ◽  
Desulfovibrio Vulgaris ◽  
Decarboxylase Activity ◽  
Sulfate Reducing ◽  
Porphobilinogen Synthase ◽  
Desulfovibrio Vulgaris Hildenborough ◽  
The Individual ◽  
Individual Enzyme ◽  
Relevant Gene

The biosynthesis of the tetrapyrrole framework has been investigated in the sulfate-reducing bacterium Desulfovibrio vulgaris Hildenborough by characterization of the enzymes required for the transformation of aminolaevulinic acid into sirohydrochlorin. PBG (porphobilinogen) synthase (HemB) was found to be a zinc-dependent enzyme that exists in its native state as a homohexamer. PBG deaminase (HemC) was shown to contain the dipyrromethane cofactor. Uroporphyrinogen III synthase is found fused with a uroporphyrinogen III methyltransferase (HemD-CobA). Both activities could be demonstrated in this amalgamated protein and the individual enzyme activities were separated by dissecting the relevant gene to allow the production of two distinct proteins. A gene annotated in the genome as a bifunctional precorrin-2 dehydrogenase/sirohydrochlorin ferrochelatase was in fact shown to act only as a dehydrogenase and is simply capable of synthesizing sirohydrochlorin rather than sirohaem. Genome analysis also reveals a lack of any uroporphyrinogen III decarboxylase, an enzyme necessary for the classical route to haem synthesis. However, the genome does encode some predicted haem d1 biosynthetic enzymes even though the bacterium does not contain the cd1 nitrite reductase. We suggest that sirohydrochlorin acts as a substrate for haem synthesis using a novel pathway that involves homologues of the d1 biogenesis system. This explains why the uroporphyrinogen III synthase is found fused with the methyltransferase, bypassing the need for uroporphyrinogen III decarboxylase activity.

scholarly journals Functional Characterization of Tissue Inhibitor of Metalloproteinase-1 (TIMP-1) N- and C-Terminal Domains duringXenopus laevisDevelopment

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
M. A. Nieuwesteeg ◽  
J. A. Willson ◽  
M. Cepeda ◽  
M. A. Fox ◽  
S. Damjanovski
Keyword(s):  
Functional Characterization ◽  
Full Length ◽  
Tissue Inhibitor Of Metalloproteinase ◽  
Tissue Inhibitors Of Metalloproteinases ◽  
Mrna Levels ◽  
Ecm Remodeling ◽  
Protein Levels ◽  
Terminal Domain ◽  
The Individual ◽  
Terminal Domains

Extracellular matrix (ECM) remodeling is essential for facilitating developmental processes. ECM remodeling, accomplished by matrix metalloproteinases (MMPs), is regulated by endogenous tissue inhibitors of metalloproteinases (TIMPs). While the TIMP N-terminal domain is involved in inhibition of MMP activity, the C-terminal domain exhibits cell-signaling activity, which is TIMP and cell type dependent. We have previously examined the distinct roles of theXenopus laevisTIMP-2 and -3 C-terminal domains during development and here examined the unique roles of TIMP-1 N- and C-terminal domains in earlyX. laevisembryos. mRNA microinjection was used to overexpress full-length TIMP-1 or its individual N- or C-terminal domains in embryos. Full-length and C-terminal TIMP-1 resulted in increased lethality compared to N-terminal TIMP-1. Overexpression of C-terminal TIMP-1 resulted in significant decreases in mRNA levels of proteolytic genes including TIMP-2, RECK, MMP-2, and MMP-9, corresponding to decreases in MMP-2 and -9 protein levels, as well as decreased MMP-2 and MMP-9 activities. These trends were not observed with the N-terminus. Our research suggests that the individual domains of TIMP-1 are capable of playing distinct roles in regulating the ECM proteolytic network during development and that the unique functions of these domains are moderated in the endogenous full-length TIMP-1 molecule.

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