scholarly journals Mapping of antigenic and functional epitopes on the alpha- and beta-subunits of two related mouse glycoproteins involved in cell interactions, LFA-1 and Mac-1.

1983 ◽  
Vol 158 (2) ◽  
pp. 586-602 ◽  
Author(s):  
F Sanchez-Madrid ◽  
P Simon ◽  
S Thompson ◽  
T A Springer
Keyword(s):  
Monoclonal Antibodies ◽  
Structural Features ◽  
Cell Interactions ◽  
Beta Subunit ◽  
Alpha Subunit ◽  
Beta Subunits ◽  
Complement Receptor ◽  
Receptor Function ◽  
Alpha Subunits ◽  
Sds Page

Mouse Mac-1, a complement receptor-associated surface structure on macrophages, and LFA-1, a function-associated structure on lymphocytes, comprise a novel family of leukocyte differentiation antigens participating in adhesive cell interactions. Mac-1 and LFA-1 contain alpha-subunits of 170,000 and 180,000 Mr, respectively, and beta-subunits of 95,000 Mr noncovalently associated in alpha 1 beta 1 complexes. The structural relation between the alpha- and between the beta-subunits, and the location of functionally important sites on the molecules, have been probed with antibodies. Both non-cross-reactive and cross-reactive monoclonal antibodies (MAb) and antisera prepared to the purified molecules or the LFA-1 alpha-subunits were used. Reactivity with individual subunits was studied by immunoprecipitation after dissociation induced by high pH treatment, or by immunoblotting after SDS-PAGE. Cross-reactive epitopes on Mac-1 and LFA-1 were found to be present on the beta-subunits, which were immunologically identical. Non-cross-reactive epitopes that are distinctive for Mac-1 or LFA-1 were localized to the alpha-subunits. MAb to LFA-1 alpha-subunit epitopes inhibited CTL-mediated killing. Two MAb to Mac-1 alpha-subunit epitopes but not a third MAb to a spatially distinct alpha-epitope inhibited complement receptor function. Neither function was inhibited by a MAb binding to a common beta-subunit epitope. Therefore, sites of Mac-1 and LFA-1 involved in their respective adhesion-related functions, as well as distinctive structural features, have been localized to the alpha-subunits.

scholarly journals A human leukocyte differentiation antigen family with distinct alpha-subunits and a common beta-subunit: the lymphocyte function-associated antigen (LFA-1), the C3bi complement receptor (OKM1/Mac-1), and the p150,95 molecule.

1983 ◽  
Vol 158 (6) ◽  
pp. 1785-1803 ◽  
Author(s):  
F Sanchez-Madrid ◽  
J A Nagy ◽  
E Robbins ◽  
P Simon ◽  
T A Springer
Keyword(s):  
Human Leukocyte ◽  
Beta Subunit ◽  
Alpha Subunit ◽  
Beta Subunits ◽  
Complement Receptor ◽  
Lymphocyte Function ◽  
Subunit Dissociation ◽  
Molecular Weights ◽  
Alpha Subunits ◽  
Sds Page

The human lymphocyte function-associated antigen-1 (LFA-1), the complement receptor-associated OKM1 molecule, and a previously undescribed molecule termed p150,95, have been found to be structurally and antigenically related. Each antigen contains an alpha- and beta-subunit noncovalently associated in an alpha 1 beta 1-structure as shown by cross-linking experiments. LFA-1, OKM1, and p150,95 alpha-subunit designations and their molecular weights are alpha L = 177,000 Mr, alpha M = 165,000 Mr, and alpha X = 150,000 Mr, respectively. The beta-subunits are all = 95,000 Mr. Some MAb precipitated only LFA-1, others only OKM1, and another precipitates all three antigens. The specificity of these MAb for particular subunits was examined after subunit dissociation by high pH. MAb specific for LFA-1 or OKM1 bind to the alpha L- or alpha M-subunits, respectively, while the cross-reactive MAb binds to the beta-subunits. Coprecipitation experiments with intact alpha 1 beta 1-complexes showed anti-alpha and anti-beta MAb can precipitate the same molecules. In two-dimensional (2D) isoelectric focusing-SDS-PAGE, the alpha subunits of the three antigens are distinct, while the beta-subunits are identical. Biosynthesis experiments showed alpha L, alpha M, and alpha X are synthesized from distinct precursors, as is beta. The three antigens differ in expression on lymphocytes, granulocytes, and monocytes. During maturation of the monoblast-like U937 line, alpha M and alpha X are upregulated and alpha L is downregulated. Some MAb to the alpha subunit of OKM1 inhibited the complement receptor type three. LFA-1, OKM1, and p150,95 constitute a novel family of functionally important human leukocyte antigens that share a common beta-subunit.

Analysis of subunit assembly of the Na-K-ATPase

1994 ◽  
Vol 266 (3) ◽  
pp. C579-C589 ◽  
Author(s):  
D. M. Fambrough ◽  
M. V. Lemas ◽  
M. Hamrick ◽  
M. Emerick ◽  
K. J. Renaud ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Sodium Pump ◽  
Beta Subunit ◽  
Alpha Subunit ◽  
Beta Subunits ◽  
Limited Region ◽  
Subunit Assembly ◽  
Alpha Subunits ◽  
Subunit Isoforms ◽  
P Type

The Na-K-ATPase, or sodium pump, is comprised of two subunits, alpha and beta. Each subunit spans the lipid bilayer of the cell membrane. This review summarizes our efforts to determine how the two subunits interact to form the functional ion transporter. Our major approach has been to observe the potential for subunit assembly when one or both subunits are truncated or present as chimeras that retain only a limited region of the Na-K-ATPase. DNAs encoding these altered subunit forms of the avian Na-K-ATPase are expressed in mammalian cells. Monoclonal antibodies specific for the avian beta-subunit are then used to purify newly synthesized avian beta-subunits, and the presence of accompanying alpha-subunits indicates that subunit assembly has occurred. The ectodomain of the beta-subunit (approximately residues 62-304) is sufficient for assembly with the alpha-subunit, and a COOH-terminal truncation of the beta-subunit that lacks aminoacyl residues beyond 162 will assemble inefficiently. A maximum of 26 aminoacyl residues of the alpha-subunit are necessary for robust assembly with the beta-subunit, when this sequence replaces the COOH-terminal half of the loop between membrane spans 7 and 8 in the SERCA1 Ca-ATPase. This region of the Ca-ATPase faces the lumen of the endoplasmic reticulum. These findings encourage study of other related questions, including whether there is preferential assembly of certain subunit isoforms and how various P-type ATPases are targeted to their appropriate subcellular compartments.

scholarly journals Protein kinase activity of the insulin receptor

1986 ◽  
Vol 235 (1) ◽  
pp. 1-11 ◽  
Author(s):  
S Gammeltoft ◽  
E Van Obberghen
Keyword(s):  
Insulin Receptor ◽  
Molecular Mechanisms ◽  
Kinase Activity ◽  
Beta Subunit ◽  
Alpha Subunit ◽  
Beta Subunits ◽  
Protein Kinase Activity ◽  
Intact Cells ◽  
Receptor Complexes ◽  
Alpha Subunits

The insulin receptor is an integral membrane glycoprotein (Mr approximately 300,000) composed of two alpha-subunits (Mr approximately 130,000) and two beta-subunits (Mr approximately 95,000) linked by disulphide bonds. This oligomeric structure divides the receptor into two functional domains such that alpha-subunits bind insulin and beta-subunits possess tyrosine kinase activity. The amino acid sequence deduced from cDNA of the single polypeptide chain precursor of human placental insulin receptor revealed that alpha- and beta-subunits consist of 735 and 620 residues, respectively. The alpha-subunit is hydrophilic, disulphide-bonded, glycosylated and probably extracellular. The beta-subunit consists of a short extracellular region which links the alpha-subunit through disulphide bridges, a hydrophobic transmembrane region and a longer cytoplasmic region which is structurally homologous with other tyrosine kinases like the src oncogene product and EGF receptor kinases. The cellular function of insulin receptors is dual: transmembrane signalling and endocytosis of hormone. The binding of insulin to its receptor on the cell membrane induces transfer of signal from extracellular to cytoplasmic receptor domains leading to activation of cell metabolism and growth. In addition, hormone-receptor complexes are internalized leading to intracellular proteolysis of insulin, whereas receptors are recycled to the membrane. These phenomena are kinetically well-characterized, but their molecular mechanisms remain obscure. Insulin receptor in different tissues and animal species are homologous in their structure and function, but show also significant differences regarding size of alpha-subunits, binding kinetics, insulin specificity and receptor-mediated degradation. We suggest that this heterogeneity of receptors may be linked to the diversity in insulin effects on metabolism and growth in various cell types. The purified insulin receptor phosphorylates its own beta-subunit and exogenous protein and peptide substrates on tyrosine residues, a reaction which is insulin-sensitive, Mn2+-dependent and specific for ATP. Tyrosine phosphorylation of the beta-subunit activates receptor kinase activity, and dephosphorylation with alkaline phosphatase deactivates the kinase. In intact cells or impure receptor preparations, a serine kinase is also activated by insulin. The cellular role of two kinase activities associated with the insulin receptor is not known, but we propose that the tyrosine- and serine-specific kinases mediate insulin actions on metabolism and growth either through dual-signalling or sequential pathways.(ABSTRACT TRUNCATED AT 400 WORDS)

Epitope-selective, monoclonal-antibody-based immunoradiometric assays of predictable specificity for differential measurement of choriogonadotropin and its subunits.

1985 ◽  
Vol 31 (8) ◽  
pp. 1322-1328 ◽  
Author(s):  
S Schwarz ◽  
P Berger ◽  
G Wick
Keyword(s):  
Monoclonal Antibody ◽  
Monoclonal Antibodies ◽  
Conformational Epitope ◽  
Alpha Subunit ◽  
Beta Subunits ◽  
Differential Measurement ◽  
Analytical Strategy ◽  
Alpha Subunits ◽  
Human Choriogonadotropin ◽  
Beta Hcg

Abstract Knowing the epitope specificities of our monoclonal antibodies (MCA) to human choriogonadotropin (hCG), we could design three classes of two-site immunoradiometric assays (IRMA): a combination of two MCA recognizing two separate alpha-epitopes (alpha-MCA) provides a system (i.e., an alpha-IRMA) that measures holo-hCG plus free alpha-subunits plus follitropin, lutropin, and thyrotropin, whereas a beta-IRMA, consisting of two beta-MCA, quantifies holo-hCG plus free beta-subunits. The amount of either of the two subunits can be calculated by subtracting the amount of holo-hCG determined in parallel in a holo-hCG-IRMA. In the latter, one of the alpha- or beta-MCA may be either cross-combined or, preferably, paired with an MCA specific for a conformational epitope. These analytical specificities, predicted from our previously established epitope map of hCG, could be experimentally verified. With these IRMAS we could demonstrate that in certain choriocarcinoma cell lines the earliest and quantitatively predominant tumor marker is the free alpha-subunit. Similar results showing an unbalanced secretion of hCG and its subunits were obtained for patients with related tumors. These findings challenge the present diagnostic practice of relying solely on "beta-hCG" radioimmunoassays and at the same time offer a novel analytical strategy.

scholarly journals Characterization of beta pat-3 heterodimers, a family of essential integrin receptors in C. elegans.

1995 ◽  
Vol 129 (4) ◽  
pp. 1127-1141 ◽  
Author(s):  
S N Gettner ◽  
C Kenyon ◽  
L F Reichardt
Keyword(s):  
Caenorhabditis Elegans ◽  
Cytoplasmic Domain ◽  
Beta Subunit ◽  
Beta Subunits ◽  
Integrin Receptors ◽  
Diverse Range ◽  
C Elegans ◽  
Alpha Subunits ◽  
Sds Page

Members of the integrin family of cell surface receptors have been shown to mediate a diverse range of cellular functions that require cell-cell or cell-extracellular matrix interactions. We have initiated the characterization of integrin receptors from the nematode Caenorhabditis elegans, an organism in which genetics can be used to study integrin function with single cell resolution. Here we report the cloning of an integrin beta subunit from C. elegans which is shown to rescue the embryonic lethal mutation pat-3(rh54) and is thus named beta pat-3. Analysis of the deduced amino acid sequence revealed that beta pat-3 is more similar to Drosophila integrin beta PS and to vertebrate integrin beta 1 than to other integrin beta subunits. Regions of highest homology are in the RGD-binding region and in the cytoplasmic domain. In addition, the 56 cysteines present in the majority of integrin beta subunits are conserved. A major transcript of approximately 3 kilo-base pairs was detected by RNA blot analysis. Immunoblot analysis using a polyclonal antiserum against the cytoplasmic domain showed that beta pat-3 migrates in SDS-PAGE with apparent M(r) of 109 k and 120 k under nonreducing and reducing conditions, respectively. At least nine protein bands with relative molecular weights in the range observed for known integrin alpha subunits coprecipitate with beta pat-3, and at least three of these bands migrate in SDS-PAGE with increased mobility when reduced. This behavior has been observed for a majority of integrin alpha subunits. Immunoprecipitations of beta pat-3 from developmentally staged populations of C. elegans showed that the expression of several of these bands changes during development. The monoclonal antibody MH25, which has been postulated to recognize the transmembrane component of the muscle dense body structure a (Francis, G. R., and R. H. Waterston. 1985. Muscle organization in Caenorhabditis elegans: localization of proteins implicated in thin filament attachment and I-band organization. J. Cell Biol. 101:1532-1549), was shown to recognize beta pat-3. Finally, immunocytochemical analysis revealed that beta pat-3 is expressed in the embryo and in many cell types postembryonically, including muscle, somatic gonad, and coelomocytes, suggesting multiple roles for integrin heterodimers containing this beta subunit in the developing animal.

scholarly journals Inherited deficiency of the Mac-1, LFA-1, p150,95 glycoprotein family and its molecular basis.

1984 ◽  
Vol 160 (6) ◽  
pp. 1901-1918 ◽  
Author(s):  
T A Springer ◽  
W S Thompson ◽  
L J Miller ◽  
F C Schmalstieg ◽  
D C Anderson
Keyword(s):  
Monoclonal Antibodies ◽  
Cell Surface ◽  
Molecular Basis ◽  
Autosomal Recessive Inheritance ◽  
Surface Expression ◽  
Beta Subunit ◽  
Beta Subunits ◽  
Normal Surface ◽  
Alpha Subunits ◽  
Deceased Patient

Leukocyte surface glycoproteins that share a common beta subunit have been found to be congenitally deficient in three unrelated patients with recurring bacterial infection. The glycoproteins, Mac-1, LFA-1, and p150,95, have the subunit compositions alpha M beta, alpha L beta, and alpha X beta, respectively. Using subunit-specific monoclonal antibodies, both the alpha M and beta subunits of Mac-1, the alpha L and beta subunits of LFA-1, and at the least the beta subunit of p150,95, were found to be deficient at the cell surface by the techniques of immunofluorescence flow cytometry, radioimmunoassay, and immunoprecipitation. A latent pool of Mac-1 that can be expressed on granulocyte surfaces in response to secretory stimuli, such as f-Met-Leu-Phe, was also lacking in patients. Deficiency was found on all leukocytes tested, including granulocytes, monocytes, and T and B lymphocytes. Quantitation by immunofluorescence cytometry of subunits on granulocytes from parents of these patients and of a fourth deceased patient showed approximately half-normal surface expression, and, together with data on other siblings and a family with an affected father and children, demonstrate autosomal recessive inheritance. Deficiency appears to be quantitative rather than qualitative, with two patients expressing approximately 0.5% and one patient approximately 5% of normal amounts. The latter patient had alpha beta complexes on the cell surface detectable by immunoprecipitation. Biosynthesis experiments showed the presence of normal amounts of alpha'L intracellular precursor in lymphoid lines of all three patients. Together with surface deficiency of three molecules that share a common beta subunit but have differing alpha subunits, this suggests the primary deficiency is of the beta subunit. The lack of maturation of alpha'L to alpha L and the deficiency of the alpha subunits at the cell surface and in latent pools suggests that association with the beta subunit is required for alpha subunit processing and transport to the cell surface or to latent pools. The molecular basis of this disease is discussed in light of adhesion-related functional abnormalities in patients' leukocytes and the blockade of similar functions in healthy cells by monoclonal antibodies.

scholarly journals beta-Subunit 102-104 residues are crucial to confer FSH activity to equine LH/CG but are not sufficient to confer FSH activity to human CG

2001 ◽  
Vol 169 (1) ◽  
pp. 55-63 ◽  
Author(s):  
M Chopineau ◽  
N Martinat ◽  
C Galet ◽  
F Guillou ◽  
Y Combarnous
Keyword(s):  
Amino Acid ◽  
Activity Ratio ◽  
Structural Features ◽  
Beta Subunit ◽  
Alpha Subunit ◽  
Beta Subunits ◽  
Cos Cells ◽  
The Impact

Horse LH/CG (eLH/CG) and donkey LH/CG (dkLH/CG) are strictly LH-specific in their respective homologous species. However, both bind to the FSH receptors from non-equid species, whereas the zebra hormone (zbLH/CG) does not. The FSH/LH ratio of eLH/CG and of the alphadkbetae hybrid is about tenfold higher than that of dkLH/CG and of the alphaebetadk hybrid, showing that the betae subunit contains the structural features responsible for the high FSH activity of eLH/CG. Only six amino acid positions (51, 94, 95, 102, 103 and 106) are unique to the betae subunit when compared with the betadk and betazb subunits. The Gly-Pro and Val-Phe sequences in positions 102-103 of betadk and betae respectively were swapped by site-directed mutations and the mutated beta-subunits cDNAs were cotransfected in COS cells with either alphae or alphadk subunit cDNA. Other mutations were also introduced in 102-103 dkLH/CG beta-subunit: Ala-Ala, Gly-Ala or Ala-Pro. These mutations with Ala-Ala, Gly-Ala or Ala-Pro in the 102-103 betadkLH/CG subunit did not change the FSH/LH ratio of dkLH/CG but the Gly(102)-Pro(103)-->Val(102)-Phe(103) mutation promoted a marked increase in the FSH/LH activity ratio. This was observed with the two heterodimers containing alphae or alphadk. Conversely, the Val(102)-Phe(103) mutation in betae led to a dramatic drop in FSH/LH activity ratio of eLH/CG, to a level similar to that of dkLH/CG. Since all FSHs possess a Gly residue at position 104, we introduced the Gly(102)-Pro(103)-Arg(104)-->Val(102)-Phe(103)-Gly(104) mutation in betadk with the expectation that the increase in FSH activity observed with the Gly(102)-Pro(103)-->Val(102)-Phe(103) mutation could be potentiated. In fact, the additional Arg(104)-->Gly(104) mutation was found to abolish the increase in FSH activity observed with Gly(102)-Pro(103)-->Val(102)-Phe(103). Mutations Gly(102)-Pro(103)-->Val(102)-Arg(103) or Gly(102)-Pro(103)-Lys(104)--> Val(102)-Arg(103)-Gly(104) were also introduced in human CGbeta (hCGbeta) to compare the impact of these amino acid changes in the well-studied gonadotrophin hCG. The betahCG mutants obtained, co-expressed either with the human or the horse alpha-subunit, did not display any FSH activity. In conclusion, the 102-104 sequence in eLH/CG beta-subunits appears to be of utmost importance for their binding to FSH receptors. However, these results obtained with equid beta-subunits are not transposable to other gonadotrophins as similar mutations in hCGbeta did not lead to any increase in FSH activity.

scholarly journals The existence and properties of two dimers of rat liver ecto-5′-nucleotidase

1984 ◽  
Vol 221 (2) ◽  
pp. 369-377 ◽  
Author(s):  
E M Bailyes ◽  
M Soos ◽  
P Jackson ◽  
A C Newby ◽  
K Siddle ◽  
...  
Keyword(s):  
Monoclonal Antibodies ◽  
Rat Liver ◽  
Peptide Mapping ◽  
Extracellular Domain ◽  
Enzymic Activity ◽  
Beta Subunit ◽  
Alpha Subunit ◽  
Beta Subunits ◽  
Solubilized Enzyme ◽  
Chemical Cross Linking

Immunoaffinity-purified rat liver 5′-nucleotidase contained two subunits of Mr 70 000 (alpha) and 38 000 (beta). Charge-shift electrophoresis and chemical cross-linking revealed that approx. 80% of the solubilized enzyme activity occurred as an alpha alpha-dimer of Mr 140 000. The remaining 20% was an alpha beta-dimer of Mr 108 000. The beta-subunit did not possess enzymic activity. Peptide mapping and immunoblotting with antibodies against the alpha- and beta-subunits showed that the beta-subunit was homologous with a part of the alpha-subunit. Three monoclonal antibodies against rat liver 5′-nucleotidase were characterized as binding to the extracellular domain of the enzyme. All three monoclonal antibodies and concanavalin A bound to the alpha-subunit, but no binding could be detected to the beta-subunit. It was therefore concluded that the beta-subunit was a fragment of an alpha-subunit that had lost an extracellular domain. Both forms of the enzyme occurred in freshly solubilized membrane preparations as well.

scholarly journals Investigations into the post-translational modification and mechanism of isopenicillin N:acyl-CoA acyltransferase using electrospray mass spectrometry

1993 ◽  
Vol 294 (2) ◽  
pp. 357-363 ◽  
Author(s):  
R T Aplin ◽  
J E Baldwin ◽  
P L Roach ◽  
C V Robinson ◽  
C J Schofield
Keyword(s):  
Mass Spectrometry ◽  
Electrospray Mass Spectrometry ◽  
Beta Subunit ◽  
Alpha Subunit ◽  
British Library ◽  
Beta Subunits ◽  
Post Translational Modification ◽  
Acetic Acids

Electrospray mass spectrometry (e.s.m.s.) was used to confirm the position of the post-translational cleavage of the isopenicillin N:acyl-CoA acyltransferase preprotein to give the alpha- and beta-subunits. The e.s.m.s. studies suggested partial modification of the alpha-subunit in vivo by exogenously added substituted acetic acids. E.s.m.s. has also allowed the observation in vitro of the transfer of the acyl group from several acyl-CoAs to the beta-subunit. N.m.r. data for the CoA species have been deposited as Supplementary Publication SUP 500173 (2 pages) at the British Library Document Supply Centre (DSC), Boston Spa, Wetherby, West Yorkshire LS23 7BQ, from whom copies can be obtained on the terms indicated in Biochem. J. (1993) 289, 9.

scholarly journals Molecular-mass heterogeneity of Griffonia simplicifolia lectin IV subunits. Differences in the oligosaccharide moieties in the N-terminal region

1990 ◽  
Vol 272 (2) ◽  
pp. 343-350 ◽  
Author(s):  
P V Nikrad ◽  
J R Pearlstone ◽  
M R Carpenter ◽  
R U Lemieux ◽  
L B Smillie
Keyword(s):  
Monosaccharide Composition ◽  
Unique Sequence ◽  
Beta Subunit ◽  
The Other ◽  
Alpha Subunit ◽  
Sequence Analyses ◽  
Griffonia Simplicifolia ◽  
Sds Page ◽  
Dimeric Protein ◽  
Covalently Linked

Lectin IV of Griffonia simplicifolia (Mr approximately 56,000), which has a strong affinity for both the Lewis b and Y blood-group determinants, is a dimeric protein of two subunits, alpha (29 kDa) and beta (27 kDa), separable by SDS/PAGE and containing covalently linked oligosaccharide. After digestion with N-glycanase, the protein migrates as a single band with a mobility identical with that of the beta-subunit. After cleavage with hydroxylamine of 3H-labelled, but otherwise intact, lectin, the radioactively labelled oligosaccharide was found to be associated with two blocked N-terminal peptides separable by h.p.l.c. and having identical amino acid compositions. One of these had three or four glucosamine residues per molecule, whereas the other had only one or two. Sequence analyses of these, as well as of a 21 kDa hydroxylamine-cleaved fragment and of the intact lectin pretreated with pyroglutamate aminopeptidase, have provided a unique sequence for residues 1-62 of the two subunits. Evidence is presented for two sites of N-linked oligosaccharide attachment at Asn-5 and Asn-18. Whereas the alpha-subunit has oligosaccharide linked to both sites, the beta-subunit has carbohydrate associated with only one (Asn-18). Sugar analyses of the whole lectin reveal a monosaccharide composition of (Xyl)3(Fuc)2(Man)10(GlcNAc)6, representing 6.4% of the mass of the molecule. Taken together with the susceptibility of the Asn-5 linkage (but not of Asn-18) to N-glycanase digestion, the observations indicate that the structures of the oligosaccharides at residues 5 and 18 are different.

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