1
|
Li Y, Chen PJ, Lin TY, Ting CY, Muthuirulan P, Pursley R, Ilić M, Pirih P, Drews MS, Menon KP, Zinn KG, Pohida T, Borst A, Lee CH. Neural mechanism of spatio-chromatic opponency in the Drosophila amacrine neurons. Curr Biol 2021; 31:3040-3052.e9. [PMID: 34033749 DOI: 10.1016/j.cub.2021.04.068] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 04/26/2021] [Accepted: 04/27/2021] [Indexed: 12/18/2022]
Abstract
Visual animals detect spatial variations of light intensity and wavelength composition. Opponent coding is a common strategy for reducing information redundancy. Neurons equipped with both spatial and spectral opponency have been identified in vertebrates but not yet in insects. The Drosophila amacrine neuron Dm8 was recently reported to show color opponency. Here, we demonstrate Dm8 exhibits spatio-chromatic opponency. Antagonistic convergence of the direct input from the UV-sensing R7s and indirect input from the broadband receptors R1-R6 through Tm3 and Mi1 is sufficient to confer Dm8's UV/Vis (ultraviolet/visible light) opponency. Using high resolution monochromatic stimuli, we show the pale and yellow subtypes of Dm8s, inheriting retinal mosaic characteristics, have distinct spectral tuning properties. Using 2D white-noise stimulus and reverse correlation analysis, we found that the UV receptive field (RF) of Dm8 has a center-inhibition/surround-excitation structure. In the absence of UV-sensing R7 inputs, the polarity of the RF is inverted owing to the excitatory input from the broadband photoreceptors R1-R6. Using a new synGRASP method based on endogenous neurotransmitter receptors, we show that neighboring Dm8s form mutual inhibitory connections mediated by the glutamate-gated chloride channel GluClα, which is essential for both Dm8's spatial opponency and animals' phototactic behavior. Our study shows spatio-chromatic opponency could arise in the early visual stage, suggesting a common information processing strategy in both invertebrates and vertebrates.
Collapse
Affiliation(s)
- Yan Li
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan, Republic of China
| | - Pei-Ju Chen
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan, Republic of China
| | - Tzu-Yang Lin
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan, Republic of China
| | - Chun-Yuan Ting
- Section on Neuronal Connectivity, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Pushpanathan Muthuirulan
- Section on Neuronal Connectivity, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Randall Pursley
- Signal Processing and Instrumentation Section, Division of Computational Bioscience, Center for Information Technology, National Institutes of Health, Bethesda, MD 20892, USA
| | - Marko Ilić
- Department of Biology, Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia
| | - Primož Pirih
- Department of Biology, Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia
| | - Michael S Drews
- Department Circuits-Computation-Models, Max-Planck-Institute of Neurobiology, 82152 Martinsried, Germany
| | - Kaushiki P Menon
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Kai G Zinn
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Thomas Pohida
- Signal Processing and Instrumentation Section, Division of Computational Bioscience, Center for Information Technology, National Institutes of Health, Bethesda, MD 20892, USA
| | - Alexander Borst
- Department Circuits-Computation-Models, Max-Planck-Institute of Neurobiology, 82152 Martinsried, Germany
| | - Chi-Hon Lee
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan, Republic of China.
| |
Collapse
|
2
|
Menon KP, Kulkarni V, Takemura SY, Anaya M, Zinn K. Interactions between Dpr11 and DIP-γ control selection of amacrine neurons in Drosophila color vision circuits. eLife 2019; 8:e48935. [PMID: 31692445 PMCID: PMC6879306 DOI: 10.7554/elife.48935] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 11/05/2019] [Indexed: 12/17/2022] Open
Abstract
Drosophila R7 UV photoreceptors (PRs) are divided into yellow (y) and pale (p) subtypes. yR7 PRs express the Dpr11 cell surface protein and are presynaptic to Dm8 amacrine neurons (yDm8) that express Dpr11's binding partner DIP-γ, while pR7 PRs synapse onto DIP-γ-negative pDm8. Dpr11 and DIP-γ expression patterns define 'yellow' and 'pale' color vision circuits. We examined Dm8 neurons in these circuits by electron microscopic reconstruction and expansion microscopy. DIP-γ and dpr11 mutations affect the morphologies of yDm8 distal ('home column') dendrites. yDm8 neurons are generated in excess during development and compete for presynaptic yR7 PRs, and interactions between Dpr11 and DIP-γ are required for yDm8 survival. These interactions also allow yDm8 neurons to select yR7 PRs as their appropriate home column partners. yDm8 and pDm8 neurons do not normally compete for survival signals or R7 partners, but can be forced to do so by manipulation of R7 subtype fate.
Collapse
Affiliation(s)
- Kaushiki P Menon
- Division of Biology and Biological EngineeringCalifornia Institute of TechnologyPasadenaUnited States
| | - Vivek Kulkarni
- Division of Biology and Biological EngineeringCalifornia Institute of TechnologyPasadenaUnited States
| | - Shin-ya Takemura
- Janelia Research CampusHoward Hughes Medical InstituteAshburnUnited States
| | - Michael Anaya
- Division of Biology and Biological EngineeringCalifornia Institute of TechnologyPasadenaUnited States
| | - Kai Zinn
- Division of Biology and Biological EngineeringCalifornia Institute of TechnologyPasadenaUnited States
| |
Collapse
|
3
|
Carrillo RA, Özkan E, Menon KP, Nagarkar-Jaiswal S, Lee PT, Jeon M, Birnbaum ME, Bellen HJ, Garcia KC, Zinn K. Control of Synaptic Connectivity by a Network of Drosophila IgSF Cell Surface Proteins. Cell 2016; 163:1770-1782. [PMID: 26687361 DOI: 10.1016/j.cell.2015.11.022] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Revised: 09/27/2015] [Accepted: 11/10/2015] [Indexed: 12/16/2022]
Abstract
We have defined a network of interacting Drosophila cell surface proteins in which a 21-member IgSF subfamily, the Dprs, binds to a nine-member subfamily, the DIPs. The structural basis of the Dpr-DIP interaction code appears to be dictated by shape complementarity within the Dpr-DIP binding interface. Each of the six dpr and DIP genes examined here is expressed by a unique subset of larval and pupal neurons. In the neuromuscular system, interactions between Dpr11 and DIP-γ affect presynaptic terminal development, trophic factor responses, and neurotransmission. In the visual system, dpr11 is selectively expressed by R7 photoreceptors that use Rh4 opsin (yR7s). Their primary synaptic targets, Dm8 amacrine neurons, express DIP-γ. In dpr11 or DIP-γ mutants, yR7 terminals extend beyond their normal termination zones in layer M6 of the medulla. DIP-γ is also required for Dm8 survival or differentiation. Our findings suggest that Dpr-DIP interactions are important determinants of synaptic connectivity.
Collapse
Affiliation(s)
- Robert A Carrillo
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA
| | - Engin Özkan
- Dept. of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL.,Howard Hughes Medical Institute, Depts. of Molecular and Cellular Physiology and Structural Biology, Stanford University School of Medicine, Stanford, CA
| | - Kaushiki P Menon
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA
| | - Sonal Nagarkar-Jaiswal
- Howard Hughes Medical Institute, Program in Developmental Biology, Dept. of Molecular and Human Genetics, Jan and Dan Duncan Neurological Research Institute at TCH, Baylor College of Medicine, Houston, TX
| | - Pei-Tseng Lee
- Howard Hughes Medical Institute, Program in Developmental Biology, Dept. of Molecular and Human Genetics, Jan and Dan Duncan Neurological Research Institute at TCH, Baylor College of Medicine, Houston, TX
| | - Mili Jeon
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA.,Howard Hughes Medical Institute, Depts. of Molecular and Cellular Physiology and Structural Biology, Stanford University School of Medicine, Stanford, CA
| | - Michael E Birnbaum
- Howard Hughes Medical Institute, Depts. of Molecular and Cellular Physiology and Structural Biology, Stanford University School of Medicine, Stanford, CA
| | - Hugo J Bellen
- Howard Hughes Medical Institute, Program in Developmental Biology, Dept. of Molecular and Human Genetics, Jan and Dan Duncan Neurological Research Institute at TCH, Baylor College of Medicine, Houston, TX
| | - K Christopher Garcia
- Howard Hughes Medical Institute, Depts. of Molecular and Cellular Physiology and Structural Biology, Stanford University School of Medicine, Stanford, CA
| | - Kai Zinn
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA
| |
Collapse
|
4
|
Menon KP, Carrillo RA, Zinn K. Development and plasticity of the Drosophila larval neuromuscular junction. Wiley Interdiscip Rev Dev Biol 2013; 2:647-70. [PMID: 24014452 DOI: 10.1002/wdev.108] [Citation(s) in RCA: 157] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The Drosophila larval neuromuscular system is relatively simple, containing only 32 motor neurons in each abdominal hemisegment, and its neuromuscular junctions (NMJs) have been studied extensively. NMJ synapses exhibit developmental and functional plasticity while displaying stereotyped connectivity. Drosophila Type I NMJ synapses are glutamatergic, while the vertebrate NMJ uses acetylcholine as its primary neurotransmitter. The larval NMJ synapses use ionotropic glutamate receptors (GluRs) that are homologous to AMPA-type GluRs in the mammalian brain, and they have postsynaptic scaffolds that resemble those found in mammalian postsynaptic densities. These features make the Drosophila neuromuscular system an excellent genetic model for the study of excitatory synapses in the mammalian central nervous system. The first section of the review presents an overview of NMJ development. The second section describes genes that regulate NMJ development, including: (1) genes that positively and negatively regulate growth of the NMJ, (2) genes required for maintenance of NMJ bouton structure, (3) genes that modulate neuronal activity and alter NMJ growth, (4) genes involved in transsynaptic signaling at the NMJ. The third section describes genes that regulate acute plasticity, focusing on translational regulatory mechanisms. As this review is intended for a developmental biology audience, it does not cover NMJ electrophysiology in detail, and does not review genes for which mutations produce only electrophysiological but no structural phenotypes.
Collapse
Affiliation(s)
- Kaushiki P Menon
- Broad Center, Division of Biology, California Institute of Technology, Pasadena, CA, USA
| | | | | |
Collapse
|
5
|
Menon KP, Sanyal S, Habara Y, Sanchez R, Wharton RP, Ramaswami M, Zinn K. The translational repressor Pumilio regulates presynaptic morphology and controls postsynaptic accumulation of translation factor eIF-4E. Neuron 2005; 44:663-76. [PMID: 15541314 DOI: 10.1016/j.neuron.2004.10.028] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2003] [Revised: 06/26/2004] [Accepted: 10/06/2004] [Indexed: 11/21/2022]
Abstract
Translational repression by Drosophila Pumilio (Pum) protein controls posterior patterning during embryonic development. Here, we show that Pum is an important mediator of synaptic growth and plasticity at the neuromuscular junction (NMJ). Pum is localized to the postsynaptic side of the NMJ in third instar larvae and is also expressed in larval neurons. Neuronal Pum regulates synaptic growth. In its absence, NMJ boutons are larger and fewer in number, while Pum overexpression increases bouton number and decreases bouton size. Postsynaptic Pum negatively regulates expression of the translation factor eIF-4E at the NMJ, and Pum binds selectively to the 3'UTR of eIF-4E mRNA. The GluRIIa glutamate receptor is upregulated in pum mutants. These results, together with genetic epistasis studies, suggest that postsynaptic Pum modulates synaptic function via direct control of eIF-4E expression.
Collapse
Affiliation(s)
- Kaushiki P Menon
- Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA
| | | | | | | | | | | | | |
Collapse
|
6
|
Dubuque SH, Schachtner J, Nighorn AJ, Menon KP, Zinn K, Tolbert LP. Immunolocalization of synaptotagmin for the study of synapses in the developing antennal lobe of Manduca sexta. J Comp Neurol 2001; 441:277-87. [PMID: 11745650 DOI: 10.1002/cne.1412] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In the mature olfactory systems of most organisms that possess a sense of smell, synapses between olfactory receptor neurons and central neurons occur in specialized neuropil structures called glomeruli. The development of olfactory glomeruli has been studied particularly heavily in the antennal lobe of the moth Manduca sexta. In the current study, we address the development of synapses within the antennal lobe of M. sexta by reporting on the localization of synaptotagmin, a ubiquitous synaptic vesicle protein, throughout development. A cDNA clone coding for M. sexta synaptotagmin was characterized and found to encode a protein that shares 67% amino acid identity with Drosophila synaptotagmin and 56% amino acid identity with human synaptotagmin I. Conservation was especially high in the C2 domains near the C-terminus and very low near the N-terminus. A polyclonal antiserum (MSYT) was raised against the unique N-terminus of M. sexta synaptotagmin, and a monoclonal antibody (DSYT) was raised against the highly conserved C-terminus of D. melanogaster synaptotagmin. In Western blot analyses, both antibodies labeled a 60 kD protein, which very likely corresponds to synaptotagmin. On sections, both antibodies labeled known synaptic neuropils in M. sexta and yielded similar labeling patterns in the developing antennal lobe. In addition, DSYT detected synaptotagmin-like protein in three other insect species examined. Analysis of synaptotagmin labeling at the light microscopic level during development of the antennal lobe of M. sexta confirmed and extended previous electron microscopic studies. Additional synapses in the coarse neuropil and a refinement of synaptic densities in the glomeruli during the last one-third of metamorphic development were revealed.
Collapse
Affiliation(s)
- S H Dubuque
- Division of Neurobiology, Arizona Research Laboratories, University of Arizona, Tucson, AZ 85721-0077, USA
| | | | | | | | | | | |
Collapse
|
7
|
Abstract
Tyrosine kinase signaling pathways are essential for process outgrowth and guidance during nervous system development. We have examined the roles of tyrosine kinase activity in programming growth cone guidance decisions in an intact nervous system in which neurons can be individually identified. We applied the tyrosine kinase inhibitors herbimycin A and genistein to whole 40% grasshopper embryos placed in medium, or injected the inhibitors into intact grasshopper eggs. Both inhibitors caused interneuronal axons that normally would grow along the longitudinal connectives to instead leave the central nervous system (CNS) within the segmental nerve root and grow out toward the body wall muscles. In addition, herbimycin A produced pathfinding errors in which many longitudinal axons crossed the CNS midline. To study how this drug affected guidance decisions made by individual growth cones, we dye-filled the pCC interneuron, which normally extends an axon anteriorly along the ipsilateral longitudinal connective. In the presence of herbimycin A, the pCC growth cone was redirected across the anterior commissure. These phenotypes suggest that tyrosine kinase inhibition blocks a signaling mechanism that repels the growth cones of longitudinal connective neurons and prevents them from crossing the midline.
Collapse
Affiliation(s)
- K P Menon
- Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA
| | | |
Collapse
|
8
|
Menon KP, Neufeld EF. Evidence for degradation of mRNA encoding alpha-L-iduronidase in Hurler fibroblasts with premature termination alleles. Cell Mol Biol (Noisy-le-grand) 1994; 40:999-1005. [PMID: 7849567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Mutations in the gene encoding alpha-L-iduronidase (IDUA) are the cause of Hurler syndrome. Fibroblasts from patients homozygous for nonsense IDUA alleles have much reduced mRNA detectable by Northern analysis, as has been observed in many other instances of premature translation termination. Yet RT-PCR (reverse transcription followed by PCR amplification) showed a normal level of a segment covering exons 1 and 2 in Hurler cells homozygous for alleles bearing the nonsense mutations, Q70X or W402X. The 3' end of the segment was between exons 2 and 4. The results indicate that the nonsense RNA was degraded to fragment(s), independent of the position of the mutation (exon 2 or exon 9, respectively). Treatment of the cells with cycloheximide resulted in some increase of intact mRNA, suggesting that translation is required for mRNA degradation.
Collapse
Affiliation(s)
- K P Menon
- Department of Biological Chemistry, UCLA School of Medicine 90024-1737
| | | |
Collapse
|
9
|
Menon KP, Gupta A. Atypical salmonellosis: two cases of sacroiliitis. INDIAN J PATHOL MICR 1993; 36:84-6. [PMID: 8354566] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Two young adult males presented with fever, severe pain, redness, swelling over the left sacroiliac joint and inability to walk and squat. A differential diagnosis of tuberculous sacroiliitis was considered. On blood culture isolation of S. Typhi in both of them was suggestive of sacroiliitis of salmonella etiology. They recovered completely following specific antibiotic therapy, aspirin and bed rest. At recovery both showed extremely high Widal titres.
Collapse
Affiliation(s)
- K P Menon
- Department of Pathology, Command Hospital Air Force Bangalore
| | | |
Collapse
|
10
|
Abstract
Mucopolysaccharidosis I (MPS I) is a lysosomal storage disease caused by deficiency of alpha-L-iduronidase. In addition to the well-known human forms (Hurler, Hurler/Scheie, and Scheie syndromes), there exists a canine model of the disease. By using previously described canine cDNA encoding alpha-L-iduronidase as a probe, the canine IDUA gene has been cloned and characterized. It contains 14 exons spread over 13 kb. An unusual GC dinucleotide was found at the donor splice site of intron 11. A transcriptional start site was identified by primer extension 177 bp upstream of the initiator AUG codon. The upstream region was found to be similar to the promoter region of many housekeeping genes: it is GC rich and has seven potential Sp1 binding sites but no TATA box or CAAT motif. The mutation in canine MPS I was localized to the area of intron 1 by RT-PCR, identified by sequence analysis of amplified genomic DNA, and confirmed by restriction analysis; it is a G-->A transition in the donor splice site of intron 1. The mutation causes retention of intron 1 in the RNA and creates a premature termination codon at the exon-intron junction.
Collapse
Affiliation(s)
- K P Menon
- Department of Biological Chemistry, School of Medicine, University of California, Los Angeles 90024-1737
| | | | | |
Collapse
|
11
|
Stoltzfus LJ, Sosa-Pineda B, Moskowitz SM, Menon KP, Dlott B, Hooper L, Teplow DB, Shull RM, Neufeld EF. Cloning and characterization of cDNA encoding canine alpha-L-iduronidase. mRNA deficiency in mucopolysaccharidosis I dog. J Biol Chem 1992; 267:6570-5. [PMID: 1551868] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
alpha-L-Iduronidase is a lysosomal enzyme, the deficiency of which causes mucopolysaccharidosis I (MPS I); a canine MPS I colony has been bred to test therapeutic intervention. The enzyme was purified to apparent homogeneity from canine testis and found to consist of two electrophoretically separable proteins that had common internal peptides but differed at their amino termini. A 57-base oligonucleotide, corresponding to the most probable codons of the longest peptide, was used to screen a canine testis cDNA library. Three cDNAs were isolated, two of which lacked the 5'-end whereas the third was full-length except for a small internal deletion. The composite sequence encodes an open reading frame of 655 amino acids that includes all sequenced peptides. The amino terminus of the larger protein, glutamic acid 26, is at the predicted signal peptide cleavage site, whereas the amino terminus of the smaller protein is leucine 106. There are six potential N-glycosylation sites and a non-canonical polyadenylation signal, CTTAAA. A search of GenBank showed that the amino acid sequence of alpha-L-iduronidase has similarity to that of a bacterial beta-xylosidase. A full-length cDNA corresponding to the composite sequence was constructed (pcIdu) and inserted into the pSVL expression vector (pSVcIdu). Two days after Cos-1 cells were transfected with pSVcIdu, their intracellular and secreted level of alpha-L-iduronidase activity has increased 8- and 22-fold, respectively, over the endogenous activity. Fibroblasts of MPS I dogs, which have no alpha-L-iduronidase activity, lacked the normal alpha-L-iduronidase mRNA of 2.2 kilobases and contained instead a trace amount of a 2.8-kilobase species. Isolation and characterization of an expressible alpha-L-iduronidase cDNA represents the first step toward mutation analysis and replacement therapy.
Collapse
Affiliation(s)
- L J Stoltzfus
- Department of Biological Chemistry, School of Medicine, University of California, Los Angeles 90024
| | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Abstract
The araC gene of Escherichia coli encodes a protein that binds the inducer L-arabinose to activate the transcription of three ara operons. In a study to determine the functional domains within the AraC protein, we have generated a set of overlapping deletions from the proximal end of the araC gene. We found that the removal of up to nearly 60% of the coding sequence of this protein still allows transcriptional activation of the ara operons in vivo, up to 27% that of the wild type. These truncated proteins, however, no longer require arabinose for induction. The ligand-induced conformational change apparently either releases or unmasks an existing functional domain within AraC, rather than generating a new conformation that is required for activation of the promoter of araBAD. Since the truncated protein of the mutant C154 (which lacks 153 amino acid residues from the N terminus) retains DNA binding specificity, the DNA-recognition domain is localized in the C-terminal half of the AraC protein. Truncated proteins were unable to repress araBAD or araC in vivo, even though they were able to bind all ara operators. We propose that the N-terminal half of AraC is essential for the formation of the DNA loops that are responsible for repression of araBAD and for autoregulation of araC.
Collapse
Affiliation(s)
- K P Menon
- Department of Biological Sciences, University of California, Santa Barbara 93106
| | | |
Collapse
|
13
|
Abstract
Several attacks of ventricular tachycardia (VT) were observed in a fifteen-year-old girl at late pregnancy. Left sided Bell's Palsy was the accompanying presentation. The symptom started with a viral-like illness. The VT could be effectively controlled with IV Lidocaine therapy. Labor was induced and the delivery was uneventful. To the best of the authors' knowledge, this syndrome was not previously described.
Collapse
|