scholarly journals Functional Mapping of an Oligomeric Autotransporter Adhesin of Aggregatibacter actinomycetemcomitans

2008 ◽  
Vol 190 (9) ◽  
pp. 3098-3109 ◽  
Author(s):  
Chunxiao Yu ◽  
Teresa Ruiz ◽  
Christopher Lenox ◽  
Keith P. Mintz
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Matrix Protein ◽  
Aggregatibacter Actinomycetemcomitans ◽  
Binding Activity ◽  
Extracellular Matrix Protein ◽  
Deletion Mutants ◽  
Mature Protein ◽  
Collagen Binding ◽  
Transmission Electron

ABSTRACT Extracellular matrix protein adhesin A (EmaA) is a 202-kDa nonfimbrial adhesin, which mediates the adhesion of the oral pathogen Aggregatibacter actinomycetemcomitans to collagen. EmaA oligomers form surface antenna-like protrusions consisting of a long helical rod with an ellipsoidal ending. The functional analysis of in-frame emaA deletion mutants has located the collagen binding activity to the amino terminus of the protein corresponding to amino acids 70 to 386. The level of collagen binding of this deletion mutant was comparable to the emaA mutant strain. Transmission electron microscopy studies indicate that the first 330 amino acids of the mature protein form the ellipsoidal ending of the EmaA protrusions, where the activity resides. Amino acid substitution analysis within this sequence has identified a critical amino acid, which is essential for the formation of the ellipsoidal ending and for collagen binding activity.

scholarly journals The primary structure of the VLA-2/collagen receptor alpha 2 subunit (platelet GPIa): homology to other integrins and the presence of a possible collagen-binding domain.

1989 ◽  
Vol 109 (1) ◽  
pp. 397-407 ◽  
Author(s):  
Y Takada ◽  
M E Hemler
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Sequence ◽  
Matrix Protein ◽  
Transmembrane Domain ◽  
Cdna Clones ◽  
Terminal Sequence ◽  
Collagen Binding ◽  
Collagen Receptor ◽  
Integrin Family

VLA-2 (also called gpIa/IIa on platelets) is a collagen receptor with a unique alpha subunit and a beta subunit common to other adhesion receptors in the VLA/integrin family. Multiple cDNA clones for the human VLA-2 alpha 2 subunit have been selected from a lambda gtll library by specific antibody screening. The 5,374-bp nucleotide sequence encoded for 1,181 amino acids, including a signal peptide of 29 amino acids followed by a long extracellular domain (1,103 amino acids), a transmembrane domain, and a short cytoplasmic segment (22 amino acids). Direct sequencing of purified alpha 2 protein confirmed the identity of the 15 NH2-terminal amino acids. Overall, the alpha 2 amino acid sequence was 18-25% similar to the sequences known for other integrin alpha subunits. In particular, the alpha 2 sequence matched other integrin alpha chains in (a) the positions of 17 of its 20 cysteine residues; (b) the presence of three metal-binding domains of the general structure DXDXDGXXD; and (c) the transmembrane domain sequence. In addition, the alpha 2 sequence has a 191-amino acid insert (called the I-domain), previously found only in leukocyte integrins of the beta 2 integrin family. The alpha 2 I-domain was 23-41% similar to domains in cartilage matrix protein and von Willebrand factor, which are perhaps associated with collagen binding. The NH2-terminal sequence reported here for alpha 2 does not match the previously reported alpha 2 NH2-terminal sequence (Takada, Y., J. L. Strominger, and M. E. Hemler. 1987. Proc. Natl. Acad. Sci. USA. 84:3239-3243). Resolution of this discrepancy suggests that there may be another VLA heterodimer that resembles VLA-2 in size but has a different amino acid sequence.

scholarly journals Glycosylation of the Collagen Adhesin EmaA of Aggregatibacter actinomycetemcomitans Is Dependent upon the Lipopolysaccharide Biosynthetic Pathway

2010 ◽  
Vol 192 (5) ◽  
pp. 1395-1404 ◽  
Author(s):  
Gaoyan Tang ◽  
Keith P. Mintz
Keyword(s):  
Matrix Protein ◽  
Sodium Dodecyl ◽  
Sugar Transport ◽  
Coiled Coil ◽  
Aggregatibacter Actinomycetemcomitans ◽  
Rabbit Heart ◽  
Extracellular Matrix Protein ◽  
Aggregation State ◽  
Collagen Binding

ABSTRACT The human oropharyngeal pathogen Aggregatibacter actinomycetemcomitans synthesizes multiple adhesins, including the nonfimbrial extracellular matrix protein adhesin A (EmaA). EmaA monomers trimerize to form antennae-like structures on the surface of the bacterium, which are required for collagen binding. Two forms of the protein have been identified, which are suggested to be linked with the type of O-polysaccharide (O-PS) of the lipopolysaccharide (LPS) synthesized (G. Tang et al., Microbiology 153:2447-2457, 2007). This association was investigated by generating individual mutants for a rhamnose sugar biosynthetic enzyme (rmlC; TDP-4-keto-6-deoxy-d-glucose 3,5-epimerase), the ATP binding cassette (ABC) sugar transport protein (wzt), and the O-antigen ligase (waaL). All three mutants produced reduced amounts of O-PS, and the EmaA monomers in these mutants displayed a change in their electrophoretic mobility and aggregation state, as observed in sodium dodecyl sulfate (SDS)-polyacrylamide gels. The modification of EmaA with O-PS sugars was suggested by lectin blots, using the fucose-specific Lens culinaris agglutinin (LCA). Fucose is one of the glycan components of serotype b O-PS. The rmlC mutant strain expressing the modified EmaA protein demonstrated reduced collagen adhesion using an in vitro rabbit heart valve model, suggesting a role for the glycoconjugant in collagen binding. These data provide experimental evidence for the glycosylation of an oligomeric, coiled-coil adhesin and for the dependence of the posttranslational modification of EmaA on the LPS biosynthetic machinery in A. actinomycetemcomitans.

scholarly journals In vivo anti-influenza virus activity of a zinc finger peptide.

1997 ◽  
Vol 41 (3) ◽  
pp. 687-692 ◽  
Author(s):  
A K Judd ◽  
A Sanchez ◽  
D J Bucher ◽  
J H Huffman ◽  
K Bailey ◽  
...  
Keyword(s):  
Amino Acids ◽  
Influenza Virus ◽  
Amino Acid ◽  
Virus Infection ◽  
Zinc Finger ◽  
Matrix Protein ◽  
H3n2 Virus ◽  
Arterial Oxygen ◽  
Treatment Schedule ◽  
Zinc Finger Peptide

Matrix protein (M1) is a major structural protein of influenza virus, and it inhibits its own polymerase. A 19-amino-acid peptide, corresponding to a zinc finger region of the M1 sequence of influenza virus strain A/PR/8/34 (H1N1), centered around amino acids 148 to 166, was synthesized. This peptide, designated peptide 6, represents a zinc finger which includes a 7-amino-acid loop or finger and a 4-amino-acid tail at the carboxyl terminus, in addition to the 8 amino acids involved in the coordination of Zn. Three experiments were run to evaluate the activity of peptide 6 on infections induced in mice by influenza A/PR/8/34 and A/Victoria/3/75 (H3N2) viruses. Intranasal (i.n.) treatment of the H1N1 virus infection with 30 or 60 mg/kg of body weight/day, three times daily for 5 days, beginning 4 h pre-or 8 h post-virus exposure, was effective in preventing death, reducing the arterial oxygen decline, and inhibiting lung consolidation. Virus titers in the lungs determined on day 5 were reduced by up to 1.5 log10 in treated groups, but considerable variation in the titers of the recovered virus was seen. The H3N2 virus infection was treated i.n. with 30, 60, or 120 mg of peptide 6/kg/day by using the above-mentioned delayed initiation treatment schedule, and similar protection was seen, although lung virus titers were not reduced in the day-5 assay. Peptide 6 was well tolerated at doses up to 60 mg/kg/day. This zinc finger peptide may provide a new class of antivirals effective against influenza virus.

Asporin competes with decorin for collagen binding, binds calcium and promotes osteoblast collagen mineralization

2009 ◽  
Vol 423 (1) ◽  
pp. 53-59 ◽  
Author(s):  
Sebastian Kalamajski ◽  
Anders Aspberg ◽  
Karin Lindblom ◽  
Dick Heinegård ◽  
Åke Oldberg
Keyword(s):  
Matrix Protein ◽  
Collagen Type I ◽  
Full Length ◽  
Extracellular Matrix Protein ◽  
Type I ◽  
Similar System ◽  
Collagen Binding ◽  
Osteoblastic Activity ◽  
Collagen Mineralization

The interactions of the ECM (extracellular matrix) protein asporin with ECM components have previously not been investigated. Here, we show that asporin binds collagen type I. This binding is inhibited by recombinant asporin fragment LRR (leucine-rich repeat) 10–12 and by full-length decorin, but not by biglycan. We demonstrate that the polyaspartate domain binds calcium and regulates hydroxyapatite formation in vitro. In the presence of asporin, the number of collagen nodules, and mRNA of osteoblastic markers Osterix and Runx2, were increased. Moreover, decorin or the collagen-binding asporin fragment LRR 10–12 inhibited the pro-osteoblastic activity of full-length asporin. Our results suggest that asporin and decorin compete for binding to collagen and that the polyaspartate in asporin directly regulates collagen mineralization. Therefore asporin has a role in osteoblast-driven collagen biomineralization activity. We also show that asporin can be expressed in Escherichia coli (Rosetta-gami™) with correctly positioned cysteine bridges, and a similar system can possibly be used for the expression of other SLRPs (small LRR proteoglycans/proteins).

scholarly journals The vitronectin-binding function of PAI-1 exacerbates lung fibrosis in mice

Blood ◽  
2011 ◽  
Vol 118 (8) ◽  
pp. 2313-2321 ◽  
Author(s):  
Anthony J. Courey ◽  
Jeffrey C. Horowitz ◽  
Kevin K. Kim ◽  
Timothy J. Koh ◽  
Margaret L. Novak ◽  
...  
Keyword(s):  
Animal Studies ◽  
Matrix Protein ◽  
Binding Capacity ◽  
Critical Role ◽  
Plasminogen Activator Inhibitor ◽  
Binding Activity ◽  
Extracellular Matrix Protein ◽  
Plasminogen Activator Inhibitor 1 ◽  
Binding Function ◽  
Pai 1

Abstract Plasminogen activator inhibitor-1 (PAI-1) is increased in the lungs of patients with pulmonary fibrosis, and animal studies have shown that experimental manipulations of PAI-1 levels directly influence the extent of scarring that follows lung injury. PAI-1 has 2 known properties that could potentiate fibrosis, namely an antiprotease activity that inhibits the generation of plasmin, and a vitronectin-binding function that interferes with cell adhesion to this extracellular matrix protein. To determine the relative importance of each PAI-1 function in lung fibrogenesis, we administered mutant PAI-1 proteins that possessed either intact antiprotease or vitronectin-binding activity to bleomycin-injured mice genetically deficient in PAI-1. We found that the vitronectin-binding capacity of PAI-1 was the primary determinant required for its ability to exacerbate lung scarring induced by intratracheal bleomycin administration. The critical role of the vitronectin-binding function of PAI-1 in fibrosis was confirmed in the bleomycin model using mice genetically modified to express the mutant PAI-1 proteins. We conclude that the vitronectin-binding function of PAI-1 is necessary and sufficient in its ability to exacerbate fibrotic processes in the lung.

scholarly journals Total 4EBP1 Is Elevated in Liver of Rats in Response to Low Sulfur Amino Acid Intake

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Angelos K. Sikalidis ◽  
Kevin M. Mazor ◽  
Minji Kang ◽  
Hongyun Liu ◽  
Martha H. Stipanuk
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Dietary Treatment ◽  
Binding Activity ◽  
Initiation Factor ◽  
Sulfur Amino Acid ◽  
Sulfur Amino Acids ◽  
Protein Levels ◽  
Cellular Stresses

Translation initiation is known to be regulated by the binding of eukaryotic initiation factor 4E (eIF4E) by binding proteins (4EBPs), and there is evidence that amino acid deprivation and other cellular stresses upregulate 4EBP1 expression. To pursue the question of whether diets limited in an essential amino acid lead to induction of 4EBP1 expression in vivo, diets that varied in methionine and cystine content were fed to rats for 7 days, and 4EBP1 mRNA and protein levels and 4EBP1 phosphorylation state were determined. Total 4EBP1 mRNA and protein abundance increased in liver of rats with severely deficient intakes of sulfur amino acids (0.23% or 0.11% methionine without cystine) but not in animals with a less restricted intake of sulfur amino acids (0.11% methionine plus 0.35% cystine) but a similarly restricted intake of total diet (53 to 62% of control). The amount of 4EBP1 binding activity (α + β forms) was elevated in liver of rats fed sulfur amino acid-deficient diets, whereas the hyperphosphorylation of 4EBP1 was not affected by dietary treatment. Results suggest that changes in total 4EBP1 expression should be considered when examining mechanisms that attenuate protein synthesis during amino acid deficiency states.

scholarly journals Amino acid sequence of HSP-1, a major protein of stallion seminal plasma: effect of glycosylation on its heparin- and gelatin-binding capabilities

1995 ◽  
Vol 310 (2) ◽  
pp. 615-622 ◽  
Author(s):  
J J Calvete ◽  
K Mann ◽  
W Schäfer ◽  
L Sanz ◽  
M Reinert ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Sequence ◽  
Seminal Plasma ◽  
Binding Activity ◽  
Size Exclusion ◽  
Major Protein ◽  
Heparin Binding ◽  
Aggregation State ◽  
Consensus Pattern

We report the complete amino acid sequence of HSP-1, a major protein isolated from stallion seminal plasma or acid extracts of ejaculated spermatozoa. The protein consists of 121 amino acids organized in two types of homologous repeats arranged in the pattern AA‘BB’. Each of the 13-15-residue A-type repeats contains two O-linked oligosaccharide chains. The B-type repeats span 44-47 amino acids each, are not glycosylated, and have the consensus pattern of the gelatin-binding fibronectin type-II module. This domain also occurs in the major bovine seminal plasma heparin-binding proteins PDC-109 (BSP-A1/A2) and BSP-A3. However, unlike the bovine proteins which bind quantitatively to a heparin-Sepharose column, stallion HSP-1 was recovered in both the flow-through and the heparin-bound fractions. Structural analysis showed that the two HSP-1 forms contain identical polypeptide chains which are differently glycosylated. Moreover, size-exclusion chromatography showed that heparin-bound HSP-1 associates with HSP-2, another major seminal plasma protein, into a 90 kDa product, whereas the non-heparin-bound glycoform of HSP-1 is eluted as a monomeric (14 kDa) protein. This suggests that glycosylation may have an indirect effect on the heparin-binding ability of HSP-1 through modulation of its aggregation state. On the other hand, both glycoforms of HSP-1 displayed gelatin-binding activity, indicating that the molecular determinants for binding heparin and gelatin are different.

Globular domains of agrin are functional units that collaborate to induce acetylcholine receptor clustering

1999 ◽  
Vol 112 (8) ◽  
pp. 1213-1223 ◽  
Author(s):  
T. Cornish ◽  
J. Chi ◽  
S. Johnson ◽  
Y. Lu ◽  
J.T. Campanelli
Keyword(s):  
Amino Acid ◽  
Acetylcholine Receptors ◽  
Matrix Protein ◽  
Extracellular Matrix Protein ◽  
Physical Separation ◽  
Surface Receptors ◽  
Physical Interactions ◽  
Functional Units ◽  
Covalently Linked ◽  
Achr Clustering

Agrin, an extracellular matrix protein involved in neuromuscular junction formation, directs clustering of postsynaptic molecules, including acetylcholine receptors (AChRs). This activity resides entirely in the C-terminal portion of the protein, which consists of three laminin-like globular domains (G-domains: G1, G2 and G3) and four EGF-like repeats. Additionally, alternate mRNA splicing yields G-domain variants G2(0,4) with 0- or 4-amino-acid inserts, and G3(0, 8,11,19) with 0-, 8-, 11- or 19-amino-acid inserts. In order to better understand the contributions of individual domains and alternate splicing to agrin activity, single G-domains and covalently linked pairs of G-domains were expressed as soluble proteins and their AChR clustering activity measured on cultured C2 myotubes. These analyses reveal the following: (1) While only G3(8) exhibits detectable activity by itself, all G-domains studied (G1, G2(0), G2(4), G3(0) and G3(8)) enhance G3(8) activity when physically linked to G3(8). This effect is most pronounced when G2(4) is linked to G3(8) and is independent of the order of the G-domains. (2) The deletion of EGF-like repeats enhances activity. (3) Increasing the physical separation between linked G1 and G3(8) domains produces a significant increase in activity; similar alterations to linked G2 and G3(8) domains are without effect. (4) Clusters induced by two concatenated G3(8) domains are significantly smaller than all other agrin forms studied. These data suggest that agrin G-domains are the functional units which interact independently of their specific organization to yield AChR clustering. G-domain synergism resulting in biological output could be due to physical interactions between G-domains or, alternatively, independent interactions of G-domains with cell surface receptors which require spatially localized coactivation for optimal signal transduction.

A 31-amino-acid N-terminal extension regulates c-Crk binding to tyrosine-phosphorylated proteins

1993 ◽  
Vol 13 (12) ◽  
pp. 7295-7302
Author(s):  
J E Fajardo ◽  
R B Birge ◽  
H Hanafusa
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Binding Affinity ◽  
Egf Receptor ◽  
Cell Transformation ◽  
Binding Activity ◽  
Sh2 Domain ◽  
Translational Initiation ◽  
Phosphorylated Proteins

Overproduction of v-Crk, but not of c-Crk, in chicken embryo fibroblasts results in cell transformation. The transforming activity of v-Crk mutants correlates with their ability to cause increased tyrosine phosphorylation of specific cellular proteins, a property that depends on the binding of v-Crk to phosphotyrosine residues via its SH2 domain. In this study, proteins translated in rabbit reticulocyte lysates were used to analyze interactions between Crk derivatives and tyrosine-phosphorylated proteins, particularly the epidermal growth factor (EGF) receptor. The results demonstrate that the binding affinity of c-Crk is much lower than that of v-Crk, despite the fact that both proteins contain identical SH2 domains. Moreover, a 31-amino-acid N-terminal extension of c-Crk, resulting from upstream translational initiation at a CUG codon, significantly increases the ability of the resulting protein to bind to phosphotyrosine-containing proteins. Of those 31 amino acids, 24 can be found in the 27-amino-acid region between Gag and Crk sequences in v-Crk, and removal of this region results in a protein with lower affinity toward the EGF receptor. In addition, fusion of Gag to the amino terminus of c-Crk yields a protein with a binding activity that is lower than that of v-Crk but significantly higher than that of c-Crk without the fusion. These data suggest that sequences N terminal to the Crk SH2 regulate binding activity to tyrosine-phosphorylated proteins and that the amino acids encoded immediately 5' to the c-Crk initiator AUG specifically increase binding affinity. In contrast, deletion of one or two SH3 domains of c-Crk proteins did not change their affinity for the EGF receptor. These results were confirmed in vivo by using A431-derived cell lines overproducing either the chicken c-Crk protein or c-Crk with the 31-amino-acid N-terminal extension. Furthermore, the in vivo experiments suggest that binding of Crk proteins to the stimulated EGF receptor results in Crk phosphorylation and subsequent loss of binding affinity.

scholarly journals Mode of Expression and Functional Characterization of FCT-3 Pilus Region-Encoded Proteins in Streptococcus pyogenes Serotype M49

2008 ◽  
Vol 77 (1) ◽  
pp. 32-44 ◽  
Author(s):  
Masanobu Nakata ◽  
Thomas Köller ◽  
Karin Moritz ◽  
Deborah Ribardo ◽  
Ludwig Jonas ◽  
...  
Keyword(s):  
Protein Expression ◽  
Streptococcus Pyogenes ◽  
Matrix Protein ◽  
Expression Patterns ◽  
Functional Characterization ◽  
T Antigen ◽  
Signal Peptidase ◽  
Extracellular Matrix Protein ◽  
Collagen Binding ◽  
Signal Peptidase I

ABSTRACT The human pathogen Streptococcus pyogenes (group A streptococcus [GAS]) pilus components, suggested to play a role in pathogenesis, are encoded in the variable FCT (fibronectin- and collagen-binding T-antigen) region. We investigated the functions of sortase A (SrtA), sortase C2 (SrtC2), and the FctA protein of the most prevalent type 3 FCT region from a serotype M49 strain. Although it is considered a housekeeping sortase, SrtA's activity is involved in pilus formation in addition to its essentiality for GAS extracellular matrix protein binding, host cell adherence/internalization, survival in human blood, and biofilm formation. SrtC2 activity is crucial for pilus formation but dispensable for the other phenotypes tested in vitro. FctA is the major pilus backbone protein, simultaneously acting as the M49 T antigen, and requires SrtC2 and LepA, a signal peptidase I homologue, for monomeric surface expression and polymerization, respectively. Collagen-binding protein Cpa expression supports pilus formation at the pilus base. Immunofluorescence microscopy and fluorescence-activated cell sorting analysis revealed several unexpected expression patterns, as follows: (i) the monomeric pilus protein FctA was found exclusively at the old poles of GAS cells, (ii) FctA protein expression increased with lower temperatures, and (iii) FctA protein expression was restricted to 20 to 50% of a given GAS M49 population, suggesting regulation by a bistability mode. Notably, disruption of pilus assembly by sortase deletion rendered GAS serotype M49 significantly more aggressive in a dermonecrotic mouse infection model, indicating that sortase activity and, consequently, pilus expression allow a subpopulation of this GAS serotype to be less aggressive. Thus, pilus expression may not be a virulence attribute of GAS per se.

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