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Head Domain (head + domain)

Distribution by Scientific Domains

Life Sciences	44%
Chemistry	33%
Medical Sciences	22%

Selected Abstracts

Actin and myosin in Gregarina polymorpha

CYTOSKELETON, Issue 2 2004
Matthew B. Heintzelman
Abstract Actin and two class XIV unconventional myosins have been cloned from Gregarina polymorpha, a large protozoan parasite inhabiting the gut of the mealworm Tenebrio molitor. These proteins were most similar to their homologues expressed in the coccidian and haemosporidian Apicomplexa such as Toxoplasma and Plasmodium despite the significant morphological differences among these parasites. Both actin and G. polymorpha myosin A (GpMyoA), a 92.6-kDa protein characterized by a canonical myosin head domain and short, highly basic tail, localized to both the longitudinally-disposed surface membrane folds (epicytic folds) of the parasite as well as to the subjacent rib-like myonemes that gird the parasite cortex. G. polymorpha myosin B (GpMyoB), a 96.3-kDa myosin, localized exclusively to the epicytic folds of the parasite. Both myosins were tightly associated with the cortical cytoskeleton and were solubilized only with a combination of high salt and detergent. Both GpMyoA and GpMyoB could bind to actin in an ATP-sensitive fashion. The distribution of actin and the unconventional myosins in G. polymorpha was consistent with their proposed participation in both the rapid (1,10 ,m/sec) gliding motility exhibited by the gregarines as well as the myoneme-mediated bending motions that have been observed in these parasites. Cell Motil. Cytoskeleton 58:83,95, 2004. © 2004 Wiley-Liss, Inc. [source]

Phosphorylation and reorganization of vimentin by p21-activated kinase (PAK)

GENES TO CELLS, Issue 2 2002
Hidemasa Goto
Background: Intermediate filament (IF) is one of the three major cytoskeletal filaments. Vimentin is the most widely expressed IF protein component. The Rho family of small GTPases, such as Cdc42, Rac and Rho, are thought to control the organization of actin filaments as well as other cytoskeletal filaments. Results: We determined if the vimentin filaments can be regulated by p21-activated kinase (PAK), one of targets downstream of Cdc42 or Rac. In vitro analyses revealed that vimentin served as an excellent substrate for PAK. This phosphorylated vimentin lost the potential to form 10 nm filaments. We identified Ser25, Ser38, Ser50, Ser65 and Ser72 in the amino-terminal head domain as the major phosphorylation sites on vimentin for PAK. The ectopic expression of constitutively active PAK in COS-7 cells induced vimentin phosphorylation. Fibre bundles or granulates of vimentin were frequent in these transfected cells. However, the kinase-inactive mutant induced neither vimentin phosphorylation nor filament reorganization. Conclusion: Our observations suggest that PAK may regulate the reorganization of vimentin filaments through direct vimentin phosphorylation. [source]

A comparative molecular force spectroscopy study of homophilic JAM-A interactions and JAM-A interactions with reovirus attachment protein ,1

JOURNAL OF MOLECULAR RECOGNITION, Issue 4 2008
Sri Ram Krishna Vedula
Abstract JAM-A belongs to a family of immunoglobulin-like proteins called junctional adhesion molecules (JAMs) that localize at epithelial and endothelial intercellular tight junctions. JAM-A is also expressed on dendritic cells, neutrophils, and platelets. Homophilic JAM-A interactions play an important role in regulating paracellular permeability and leukocyte transmigration across epithelial monolayers and endothelial cell junctions, respectively. In addition, JAM-A is a receptor for the reovirus attachment protein, ,1. In this study, we used single molecular force spectroscopy to compare the kinetics of JAM-A interactions with itself and ,1. A chimeric murine JAM-A/Fc fusion protein and the purified ,1 head domain were used to probe murine L929 cells, which express JAM-A and are susceptible to reovirus infection. The bond half-life (t1/2) of homophilic JAM-A interactions was found to be shorter () than that of ,1/JAM-A interactions (). These results are in accordance with the physiological functions of JAM-A and ,1. A short bond lifetime imparts a highly dynamic nature to homophilic JAM-A interactions for regulating tight junction permeability while stable interactions between ,1 and JAM-A likely anchor the virus to the cell surface and facilitate viral entry. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Are giant axons a pathological marker of charcot-marie-tooth neuropathy type 2E?

JOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 2 2004
T Cavallaro
Background: According to electrophysiological and pathological criteria Charcot Marie Tooth (CMT) disease includes primary demyelinating forms (CMT1) and neuropathies with primary axonal loss (CMT2). In CMT1, genetic analysis provided some associations between characteristic lesions and different proteins. In CMT2, four genes were identified recently (CMT2A, B, D, E); the molecular diagnosis is complex and phenotypical hallmarks are lacking. Objectives: To describe the nerve biopsy in three pedigrees with CMT2E caused by mutations of the neurofilament-light chain gene (NF-L): two pedigrees from Campania sharing a Pro22Ser substitution in the head domain of protein and one pedigree from Apulia with a novel Leu268Prol substitution in the central rod domain. In all three pedigrees electrophysiology was consistent with a mixed, demyelinating and axonal neuropathy. Results: The three patients analysed revealed a primary axonopathy characterized by giant axonal swelling filled with densely packed neurofilaments and some atrophic axons. Conclusions: We propose that, in the diagnostic work up of CMT2, giant axons may orientate towards CMT2E. The pathological alterations detected correlate intuitively with an altered function of the neurofilaments which constitute the axonal cytoskeleton and are critical for radial growth and for axonal transport. [source]

Crystallization of the head and galectin-like domains of porcine adenovirus isolate NADC-1 fibre

ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 11 2009
Pablo Guardado-Calvo
The porcine adenovirus NADC-1 isolate, a strain of porcine adenovirus type 4, has a fibre with an atypical architecture. In addition to a classical virus-attachment region, shaft and head domains, it contains an additional galectin-like domain C-terminal to the head domain and connected to the head domain by a long RGD-containing loop. The galectin-like domain contains two putative carbohydrate-recognition domains. The head and galectin-like domains have been independently crystallized. Diffraction data have been obtained to 3.2,Å resolution from crystals of the head domain and to 1.9,Å resolution from galectin-like domain crystals. [source]

Myosin diversity in the diatom Phaeodactylum tricornutum,

CYTOSKELETON, Issue 3 2010
Matthew B. Heintzelman
Abstract This report describes the domain architecture of ten myosins cloned from the pennate diatom Phaeodactylum tricornutum. Several of the P. tricornutum myosins show similarity to myosins from the centric diatom Thalassiosira pseudonana as well as to one myosin from the oomycete Phytophthora ramorum. The P. tricornutum myosins, ranging in size from 126 kDa to over 250 kDa, all possess the canonical head, neck and tail domains common to most myosins, though variations in each of these domains is evident. Among the features distinguishing several of the diatom myosin head domains are N-terminal SH3-like domains, variations in or near the P-loop and Loop 1 regions close to the nucleotide binding pocket, and extended converter domains. Variations in the length of the neck domain or lever arm, defined by the light chain-binding IQ motifs, are apparent with the different diatom myosins predicted to contain from one to nine IQ motifs. Protein domains found within the P. tricornutum myosin tails include regions of coiled-coil structure, ankyrin repeats, CBS domain pairs, a PB1 domain, a kinase domain and a FYVE-finger motif. As many of these features have never before been characterized in myosins of any type, it is likely that these new diatom myosins will expand the repertoire of known myosin behaviors. © 2010 Wiley-Liss, Inc. [source]

Biochemical and functional characterization of the interaction between pentraxin 3 and C1q

EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 2 2003

Abstract Pentraxin 3 (PTX3) is a recently characterized member of the pentraxin family of acute-phase proteins produced during inflammation. Classical short pentraxins, C-reactive protein, and serum amyloid P component can bind to C1q and thereby activate the classical complement pathway. Since PTX3 can also bind C1q, the present study was designed to define the interaction between PTX3 and C1q and to examine the functional consequences of this interaction. A dose-dependent binding of both C1q and the C1 complex to PTX3 was observed. Experiments with recombinant globular head domains of human C1q A, B, and C chains indicated that C1q interacts with PTX3 via its globular head region. Binding of C1q to immobilized PTX3 induced activation of the classical complement pathway as assessed by C4 deposition. Furthermore, PTX3 enhanced C1q binding and complement activation on apoptotic cells. However, in the fluid-phase, pre-incubation of PTX3 with C1q resulted in inhibition of complement activation by blocking the interaction of C1q with immunoglobulins. These results indicate that PTX3 can both inhibit and activate the classical complement pathway by binding C1q, depending on the way it is presented. PTX3 may therefore be involved in the regulation of the innate immune response. [source]

Role and regulation of human XRCC4-like factor/cernunnos,

JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 5 2008
Kirsten Dahm
Abstract In mammalian cells, non-homologous end joining (NHEJ) is the major double strand break (DSB) repair mechanism during the G1 phase of the cell cycle. It also contributes to DSB repair during the S and G2 phases. Ku heterodimer, DNA PKcs, XRCC4 and DNA Ligase IV constitute the core NHEJ machinery, which joins directly ligatable ends. XRCC4-like factor/Cernunnos (XLF/Cer) is a recently discovered interaction partner of XRCC4. Current evidence suggests the following model for the role of XLF/Cer in NHEJ: after DSB induction, the XRCC4-DNA Ligase IV complex promotes efficient accumulation of XLF/Cer at DNA damage sites via constitutive interaction of the XRCC4 and XLF/Cer head domains and dependent on components of the DNA PK complex. Ku alone can stabilise the association of XLF/Cer with DNA ends. XLF/Cer stimulates ligation of complementary and non-complementary DNA ends by XRCC4-DNA Ligase IV. This activity involves the carboxy-terminal DNA binding region of XLF/Cer and could occur via different, non-exclusive modes: (i) enhancement of the stability of the XRCC4-DNA Ligase IV complex on DNA ends by XLF/Cer, (ii) modulation of the efficiency and/or specificity of DNA Ligase IV by binding of XLF/Cer to the XRCC4-DNA Ligase IV complex, (iii) promotion of the alignment of blunt or other non-complementary DNA ends by XLF/Cer for ligation. XLF/Cer promotes the preservation of 3, overhangs, restricts nucleotide loss and thereby promotes accuracy of DSB joining by XRCC4-DNA Ligase IV during NHEJ and V(D)J recombination. J. Cell. Biochem. 104: 1534,1540, 2008. © 2008 Wiley-Liss, Inc. [source]