scholarly journals Evolution of a σ–(c-di-GMP)–anti-σ switch

2021 ◽  
Vol 118 (30) ◽  
pp. e2105447118
Author(s):  
Maria A. Schumacher ◽  
Kelley A. Gallagher ◽  
Neil A. Holmes ◽  
Govind Chandra ◽  
Max Henderson ◽  
...  

Filamentous actinobacteria of the genus Streptomyces have a complex lifecycle involving the differentiation of reproductive aerial hyphae into spores. We recently showed c-di-GMP controls this transition by arming a unique anti-σ, RsiG, to bind the sporulation-specific σ, WhiG. The Streptomyces venezuelae RsiG–(c-di-GMP)2–WhiG structure revealed that a monomeric RsiG binds c-di-GMP via two E(X)3S(X)2R(X)3Q(X)3D repeat motifs, one on each helix of an antiparallel coiled-coil. Here we show that RsiG homologs are found scattered throughout the Actinobacteria. Strikingly, RsiGs from unicellular bacteria descending from the most basal branch of the Actinobacteria are small proteins containing only one c-di-GMP binding motif, yet still bind their WhiG partners. Our structure of a Rubrobacter radiotolerans (RsiG)2–(c-di-GMP)2–WhiG complex revealed that these single-motif RsiGs are able to form an antiparallel coiled-coil through homodimerization, thereby allowing them to bind c-di-GMP similar to the monomeric twin-motif RsiGs. Further data show that in the unicellular actinobacterium R. radiotolerans, the (RsiG)2–(c-di-GMP)2–WhiG regulatory switch controls type IV pilus expression. Phylogenetic analysis indicates the single-motif RsiGs likely represent the ancestral state and an internal gene-duplication event gave rise to the twin-motif RsiGs inherited elsewhere in the Actinobacteria. Thus, these studies show how the anti-σ RsiG has evolved through an intragenic duplication event from a small protein carrying a single c-di-GMP binding motif, which functions as a homodimer, to a larger protein carrying two c-di-GMP binding motifs, which functions as a monomer. Consistent with this, our structures reveal potential selective advantages of the monomeric twin-motif anti-σ factors.

Author(s):  
Taylore Dodd ◽  
Tingzhong Wang ◽  
Shetuan Zhang

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).


2021 ◽  
Author(s):  
C. R. Morton ◽  
N. J. Rzechorzek ◽  
J. D. Maman ◽  
M. Kuramochi ◽  
H. Sekiguchi ◽  
...  

AbstractThe DNA repair factor CtIP has a critical function in Double-Strand Break (DSB) repair by Homologous Recombination, promoting the assembly of the repair apparatus at DNA ends and participating in DNA-end resection. However, the molecular mechanisms of CtIP function in DSB repair remain unclear. Here we present an atomic model for the three-dimensional architecture of human CtIP, derived from a multi-disciplinary approach that includes X-ray crystallography, Small-angle X-ray Scattering (SAXS) and Diffracted X-ray Tracking (DXT). Our data show that CtIP adopts an extended dimer-of-dimers structure, in agreement with a role in bridging distant sites on chromosomal DNA during recombinational repair. The zinc-binding motif in CtIP’s N-terminus alters dynamically the coiled coil structure, with functional implications for the long-range interactions of CtIP with DNA. Our results provide a structural basis for the three-dimensional arrangement of chains in the CtIP tetramer, a key aspect of CtIP function in DNA DSB repair.


2020 ◽  
Author(s):  
Roberto Marabini ◽  
Gabriela N. Condezo ◽  
Josué Gómez-Blanco ◽  
Carmen San Martín

AbstractLittle is known about the basic biology of non-human adenoviruses, which could be alternative vectors free of issues posed by preexisting immunity to human adenoviruses. We present the cryo-EM structure of a lizard atadenovirus, LAdV-2, at 3.4 Å resolution. This is the first high resolution structure of an adenovirus with non-mammalian host, and of an adenovirus not belonging to the Mastadenovirus genus. Atadenovirus capsids contain genus specific proteins LH3, p32k, and LH2, and are more thermostable than the more studied human adenoviruses. We find a large conformational difference in the internal vertex protein IIIa between mast- and atadenoviruses, induced by the presence of an extended polypeptide in the region. This polypeptide, as well as α-helical clusters located beneath the icosahedral facet, likely correspond to proteins LH2 and p32k. The external genus specific protein LH3, with a trimeric β-helix fold typical of bacteriophage host attachment proteins, contacts the hexon shell surface via a triskelion structure identical to that used by protein IX in human AdV, revealing a conserved capsid-binding motif and a possible gene duplication event. Altogether, this work shows how the network of minor coat proteins differs between AdV genera and relates to virus evolution and capsid stability properties.


Cells ◽  
2019 ◽  
Vol 8 (10) ◽  
pp. 1146 ◽  
Author(s):  
Brown ◽  
del Corsso ◽  
Zoidl ◽  
Donaldson ◽  
Spray ◽  
...  

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.


2007 ◽  
Vol 20 (8) ◽  
pp. 966-976 ◽  
Author(s):  
Wenming Wang ◽  
Alessandra Devoto ◽  
John G. Turner ◽  
Shunyuan Xiao

The powdery mildew resistance genes RPW8.1 and RPW8.2 from Arabidopsis differ from the other isolated plant resistance (R) genes in their predicted protein domains and their resistance spectrum. The two homologous RPW8 genes encode small proteins featuring a predicted amino-terminal transmembrane anchor domain and a coiled-coil domain and confer resistance to a broad spectrum of powdery mildews. Here, we show that Arabidopsis plants expressing the RPW8 genes have enhanced resistance to another biotrophic pathogen, Hyaloperonospora parasitica, raising the possibility that the RPW8 genes may function to enhance salicylic-acid-dependent basal defenses, rather than as powdery-mildew-specific R genes. When overexpressed from their native promoters, the RPW8 genes confer enhanced resistance to the Cauliflower mosaic virus, but render plants more susceptible to the necrotrophic fungal pathogens Alternaria and Botrytis spp. Furthermore, we show that the RPW8 proteins appear to be localized to the endomembrane system, overlapping with the endoplasmic reticulum–associated small GTPase SAR1, and accumulate to higher levels in response to application of exogenous salicylic acid, one of the signaling molecules of plant defense.


Biochemistry ◽  
2018 ◽  
Vol 57 (47) ◽  
pp. 6581-6591 ◽  
Author(s):  
Fei Song ◽  
Minxing Li ◽  
Gaohua Liu ◽  
G.V.T. Swapna ◽  
Nourhan S. Daigham ◽  
...  

2007 ◽  
Vol 88 (1) ◽  
pp. 13-18 ◽  
Author(s):  
Yeun-Kyung Shin ◽  
Qiang Liu ◽  
Suresh K. Tikoo ◽  
Lorne A. Babiuk ◽  
Yan Zhou

Influenza A virus infection activates the phosphatidylinositol 3-kinase (PI3K)/Akt pathway, but the mechanism is not clear. Here, it is reported that influenza A virus NS1 protein is responsible for PI3K/Akt pathway activation. It was demonstrated that the NS1 protein interacts with the p85 regulatory subunit of PI3K via direct binding to the SH3 and C-terminal SH2 domains of p85. Consensus binding motifs for SH3 and SH2 domains were found in influenza A virus NS1, namely an SH2-binding motif (YXXXM) at aa 89, SH3-binding motif 1 (PXXP) around aa 164 and SH3-binding motif 2 around aa 212. Mutant virus encoding NS1 protein with mutations in the SH-binding motifs failed to interact with SH domains of p85 and did not activate the PI3K/Akt pathway. The mutant virus is attenuated in Madin–Darby canine kidney cells. Our study has established a novel function of NS1: by interacting with p85 via the SH-binding motifs, NS1 can activate the PI3K/Akt pathway.


2005 ◽  
Vol 3 (7) ◽  
pp. 1189 ◽  
Author(s):  
Kevin Pagel ◽  
Karsten Seeger ◽  
Bettina Seiwert ◽  
Alessandra VillaCurrent address: J. W. Goethe ◽  
Alan E. Mark ◽  
...  

2005 ◽  
Vol 25 (23) ◽  
pp. 10433-10441 ◽  
Author(s):  
Anja C. Nagel ◽  
Alena Krejci ◽  
Gennady Tenin ◽  
Alejandro Bravo-Patiño ◽  
Sarah Bray ◽  
...  

ABSTRACT Notch signal transduction centers on a conserved DNA-binding protein called Suppressor of Hairless [Su(H)] in Drosophila species. In the absence of Notch activation, target genes are repressed by Su(H) acting in conjunction with a partner, Hairless, which contains binding motifs for two global corepressors, CtBP and Groucho (Gro). Usually these corepressors are thought to act via different mechanisms; complexed with other transcriptional regulators, they function independently and/or redundantly. Here we have investigated the requirement for Gro and CtBP in Hairless-mediated repression. Unexpectedly, we find that mutations inactivating one or the other binding motif can have detrimental effects on Hairless similar to those of mutations that inactivate both motifs. These results argue that recruitment of one or the other corepressor is not sufficient to confer repression in the context of the Hairless-Su(H) complex; Gro and CtBP need to function in combination. In addition, we demonstrate that Hairless has a second mode of repression that antagonizes Notch intracellular domain and is independent of Gro or CtBP binding.


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