Characterisation of human and murine snRNP proteins by two-dimensional gel electrophoresis and phosphopeptide analysis of U1-specific 70K protein variants (original) (raw)
Journal Article
Institut für Molekularbiologie und Tumorforschung der Philipps-Universitat Marburg
Emil-Mannkopff-StraBe 2, D-3550 Marburg
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Institut für Molekularbiologie und Tumorforschung der Philipps-Universitat Marburg
Emil-Mannkopff-StraBe 2, D-3550 Marburg
Search for other works by this author on:
Institut für Molekularbiologie und Tumorforschung der Philipps-Universitat Marburg
Emil-Mannkopff-StraBe 2, D-3550 Marburg
Search for other works by this author on:
Institut für Molekularbiologie und Tumorforschung der Philipps-Universitat Marburg
Emil-Mannkopff-StraBe 2, D-3550 Marburg
Search for other works by this author on:
Institut für Molekularbiologie und Tumorforschung der Philipps-Universitat Marburg
Emil-Mannkopff-StraBe 2, D-3550 Marburg
*To whom correspondence should be addressed
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1Heinrich-Pette-lnstitut, MartinistraBe 52, D-2000 Hamburg 20
2Schering AG, MullerstraBe 170-178, D-1000 Berlin 65
3Technische Fachhochschule Berlin, SeestraBe 10, D-1000 Berlin 65, FRG
Revision received:
13 June 1990
Published:
11 August 1990
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Andreas Woppmann, Thilo Patschinsky, Peter Bringmann, Franz Godt, Reinhard Luhrmann, Characterisation of human and murine snRNP proteins by two-dimensional gel electrophoresis and phosphopeptide analysis of U1-specific 70K protein variants, Nucleic Acids Research, Volume 18, Issue 15, 11 August 1990, Pages 4427–4438, https://doi.org/10.1093/nar/18.15.4427
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Abstract
The proteins of the major human snRNPs U1, U2, U4/U6 and U5 were characterised by two-dimensional electrophoresis, with isoelectric focussing in the first dimension and SDS-polyacrylamide gel electrophoresis in the second. With the exception of protein F, which exhibits an acidic pi value (pi = 3.3), the snRNP proteins are basic. Post-translational modification was found among the proteins associated specifically with the U1 and U2 particles. The most complex modification pattern was observed for the U1-specific 70K protein. This was found in at least 13 isoelectric variants, with pi values ranging from 6.7 to 8.7; these variants differed also in molecular weight. All of the 70K variants are phosphorylated in the cell. Thin-layer analysis of their tryptic phosphopeptides revealed that the 70K variants have four major phosphopeptides in common, in addition to which at least four additional serine residues are phosphorylated to different extents. The comparative phosphopeptide analysis shows that differential phosphorylation alone is not sufficient to explain the occurrence of the many isoelectric variants of 70K, so that the final charge of the 70K variants is determined both by phosphorylation and by other, as yet unidentified posttranslational modifications. By two-dimensional separation of snRNP proteins obtained from mouse Ehrlich ascites tumour cells, it was shown that the pattern of pi values of the mouse proteins was almost identical with the corresponding pattern for human proteins. Even the complex modification patterns of the 70K protein are identical in mouse and man, indicating that the presence in the cell of so many variants of this protein may have functional importance. The major difference between murine and human snRNP proteins is the absence of protein B' from mouse snRNPs. This suggests that the homologous protein B may be able to carry out the task of protein B'.
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Author notes
1Heinrich-Pette-lnstitut, MartinistraBe 52, D-2000 Hamburg 20
2Schering AG, MullerstraBe 170-178, D-1000 Berlin 65
3Technische Fachhochschule Berlin, SeestraBe 10, D-1000 Berlin 65, FRG
© 1990 Oxford University Press
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