TWO-DIMENSIONAL ELECTROPHORESIS OF SIMIAN VIRUS 40 (SV40) TUMOR ANTIGEN TWO-DIMENSIONAL ELECTROPHORESIS OF SIMIAN VIRUS 40 (SV40) TUMOR ANTIGEN

The simian virus 40 large tumor antigen (T-ag) is found in both the nuclei (nT-ag) and plasma membranes (mT-ag) of simian virus 40-infected or -transformed cells. It is not known how newly synthesized T-ag molecules are recognized, sorted, and transported to their ultimate subcellular destinations. One possibility is that these events depend upon structural differences between nT-ag and mT-ag. To test this possibility, we compared the structures of nT-ag and mT-ag from simian virus 40-infected cells. No differences between the two forms of T-ag were detected by migration in polyacrylamide gels, by Staphylococcus aureus V8 partial proteolytic mapping of methionine- or proline-containing peptides, or by two-dimensional tryptic peptide mapping of methionine-containing peptides. The carboxy-terminal, methionine-containing tryptic peptide was identified in the two-dimensional maps and was shown to be identical in nT-ag and mT-ag. Thus, a structural basis for the recognition and differential localization of T-ags could not be demonstrated. The carboxy terminus of the T-ag encoded by mutant dlA2413 is derived from the alternate open reading frame of the simian virus 40 early region, in analogy with the theoretical early gene product, T*-ag. We used this mutant to identify peptides unique to T*-ag. None of these peptides were detected in maps of mT-ag; only wild-type T-ag-specific peptides were found. These findings suggest that T*-ag does not represent the membrane-associated form of T-ag, but that mT-ag is encoded within the same reading frame used for nT-ag.

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Absence of a structural basis for intracellular recognition and differential localization of nuclear and plasma membrane-associated forms of simian virus 40 large tumor antigen

Molecular and Cellular Biology ◽

10.1128/mcb.6.3.758-767.1986 ◽

1986 ◽

Vol 6 (3) ◽

pp. 758-767

Author(s):

D L Jarvis ◽

C N Cole ◽

J S Butel

Keyword(s):

Tumor Antigen ◽

Tryptic Peptide ◽

Simian Virus 40 ◽

Simian Virus ◽

Structural Basis ◽

Two Dimensional ◽

Large Tumor ◽

Reading Frame ◽

Large Tumor Antigen ◽

Differential Localization

The simian virus 40 large tumor antigen (T-ag) is found in both the nuclei (nT-ag) and plasma membranes (mT-ag) of simian virus 40-infected or -transformed cells. It is not known how newly synthesized T-ag molecules are recognized, sorted, and transported to their ultimate subcellular destinations. One possibility is that these events depend upon structural differences between nT-ag and mT-ag. To test this possibility, we compared the structures of nT-ag and mT-ag from simian virus 40-infected cells. No differences between the two forms of T-ag were detected by migration in polyacrylamide gels, by Staphylococcus aureus V8 partial proteolytic mapping of methionine- or proline-containing peptides, or by two-dimensional tryptic peptide mapping of methionine-containing peptides. The carboxy-terminal, methionine-containing tryptic peptide was identified in the two-dimensional maps and was shown to be identical in nT-ag and mT-ag. Thus, a structural basis for the recognition and differential localization of T-ags could not be demonstrated. The carboxy terminus of the T-ag encoded by mutant dlA2413 is derived from the alternate open reading frame of the simian virus 40 early region, in analogy with the theoretical early gene product, T*-ag. We used this mutant to identify peptides unique to T*-ag. None of these peptides were detected in maps of mT-ag; only wild-type T-ag-specific peptides were found. These findings suggest that T*-ag does not represent the membrane-associated form of T-ag, but that mT-ag is encoded within the same reading frame used for nT-ag.

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Sialic Acid Dependent Polypeptide Chain Heterogeneity of Human Fibrinogen Demonstrated by Two-Dimensional Electrophoresis

Thrombosis and Haemostasis ◽

10.1055/s-0038-1657116 ◽

1982 ◽

Vol 47 (01) ◽

pp. 019-021 ◽

Cited By ~ 13

Author(s):

Cemal Kuyas ◽

André Haeberli ◽

P Werner Straub

Keyword(s):

Sialic Acid ◽

Polypeptide Chain ◽

Two Dimensional ◽

Charge Heterogeneity ◽

Human Fibrinogen ◽

Two Dimensional Electrophoresis ◽

Isoelectric Points ◽

Polypeptide Chains ◽

Dimensional Electrophoresis ◽

Chain Type

SummaryHuman fibrinogen was compared with asialofibrinogen by two-dimensional electrophoresis to evaluate the contribution of sialic acid to the heterogeneity of the γ- and Bβ-polypeptide chains.Reduced fibrinogen showed three major variants for both the γ- and Bβ-chains. In addition two minor γ-bands with a more acidic isoelectric point than the normal γ-chains were observed. Electrophoresis in the second dimension (SDS) suggests that these most acidic bands are γ-chain-variants with a higher molecular weight. In asialofibrinogen only two predominant variants with more alkaline isoelectric points were present in each chain type.It is concluded that enzymatic removal of sialic acid partially reduces the heterogeneity of the γ- and Bβ-polypeptide chains of human fibrinogen, but additional sources producing charge heterogeneity must be sought.

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