Cleavage of the alpha 1-microglobulin-bikunin precursor is localized to the Golgi apparatus of rat liver cells
(1993) In Biochimica et Biophysica Acta 1157(2). p.54-147- Abstract
alpha 1-Microglobulin, a plasma protein with immunoregulatory properties, and bikunin, the light chain of the proteinase inhibitors inter-alpha-inhibitor and pre-alpha-inhibitor, are translated as a precursor protein from the same mRNA. The cosynthesis of alpha 1-microglobulin and bikunin is unique compared to other proproteins such as procomplement components and prohormones, since alpha 1-microglobulin and bikunin have no known functional connection. Different forms of intracellular rat liver alpha 1-microglobulin were isolated and characterized by amino acid sequence analysis, lectin binding and glycosidase treatment. Their subcellular distribution was studied by Nycodenz and sucrose gradient centrifugation, pulse-chase experiments,... (More)
alpha 1-Microglobulin, a plasma protein with immunoregulatory properties, and bikunin, the light chain of the proteinase inhibitors inter-alpha-inhibitor and pre-alpha-inhibitor, are translated as a precursor protein from the same mRNA. The cosynthesis of alpha 1-microglobulin and bikunin is unique compared to other proproteins such as procomplement components and prohormones, since alpha 1-microglobulin and bikunin have no known functional connection. Different forms of intracellular rat liver alpha 1-microglobulin were isolated and characterized by amino acid sequence analysis, lectin binding and glycosidase treatment. Their subcellular distribution was studied by Nycodenz and sucrose gradient centrifugation, pulse-chase experiments, and electrophoresis with subsequent immunoblotting, using pro-C3 and prohaptoglobin as reference proteins. Two alpha 1-microglobulin-bikunin precursors (40 and 42 kDa), containing one and two N-linked oligosaccharides, respectively, were detected in the endoplasmic reticulum. After transport to the Golgi apparatus, the precursors were cleaved, probably C-terminal to the sequence Arg-Ala-Arg-Arg immediately preceding the bikunin part, yielding free sialylated 28 kDa alpha 1-microglobulin, representing the mature protein. The cleavage was almost complete in phosphatidylinositol 4-kinase-enriched membranes, previously identified as a post-Golgi compartment. A fourth intracellular form of alpha 1-microglobulin, 26 kDa, lacked sialic acid. None of the intracellular forms carried the yellow-brown chromophore associated with alpha 1-microglobulin when purified from serum and urine, suggesting that this chromophore becomes linked to the protein after its secretion from the liver cells.
(Less)
- author
- Bratt, Tomas ; Olsson, H ; Sjöberg, E M ; Jergil, B LU and Akerström, B LU
- organization
- publishing date
- 1993-06-11
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- 1-Phosphatidylinositol 4-Kinase, Alpha-Globulins/chemistry, Animals, Cells, Cultured, Glycoproteins/metabolism, Golgi Apparatus/metabolism, Liver/metabolism, Male, Membrane Glycoproteins, Phosphotransferases/metabolism, Protein Precursors/chemistry, Rats, Rats, Sprague-Dawley, Subcellular Fractions/metabolism, Trypsin Inhibitor, Kunitz Soybean
- in
- Biochimica et Biophysica Acta
- volume
- 1157
- issue
- 2
- pages
- 54 - 147
- publisher
- Elsevier
- external identifiers
-
- pmid:7685189
- scopus:0027213232
- ISSN
- 0006-3002
- DOI
- 10.1016/0304-4165(93)90058-G
- language
- English
- LU publication?
- yes
- id
- 9d2069b3-628f-48bd-91a6-1f49569df4ff
- date added to LUP
- 2019-05-22 10:23:48
- date last changed
- 2024-06-12 16:00:44
@article{9d2069b3-628f-48bd-91a6-1f49569df4ff,
abstract = {{<p>alpha 1-Microglobulin, a plasma protein with immunoregulatory properties, and bikunin, the light chain of the proteinase inhibitors inter-alpha-inhibitor and pre-alpha-inhibitor, are translated as a precursor protein from the same mRNA. The cosynthesis of alpha 1-microglobulin and bikunin is unique compared to other proproteins such as procomplement components and prohormones, since alpha 1-microglobulin and bikunin have no known functional connection. Different forms of intracellular rat liver alpha 1-microglobulin were isolated and characterized by amino acid sequence analysis, lectin binding and glycosidase treatment. Their subcellular distribution was studied by Nycodenz and sucrose gradient centrifugation, pulse-chase experiments, and electrophoresis with subsequent immunoblotting, using pro-C3 and prohaptoglobin as reference proteins. Two alpha 1-microglobulin-bikunin precursors (40 and 42 kDa), containing one and two N-linked oligosaccharides, respectively, were detected in the endoplasmic reticulum. After transport to the Golgi apparatus, the precursors were cleaved, probably C-terminal to the sequence Arg-Ala-Arg-Arg immediately preceding the bikunin part, yielding free sialylated 28 kDa alpha 1-microglobulin, representing the mature protein. The cleavage was almost complete in phosphatidylinositol 4-kinase-enriched membranes, previously identified as a post-Golgi compartment. A fourth intracellular form of alpha 1-microglobulin, 26 kDa, lacked sialic acid. None of the intracellular forms carried the yellow-brown chromophore associated with alpha 1-microglobulin when purified from serum and urine, suggesting that this chromophore becomes linked to the protein after its secretion from the liver cells.</p>}},
author = {{Bratt, Tomas and Olsson, H and Sjöberg, E M and Jergil, B and Akerström, B}},
issn = {{0006-3002}},
keywords = {{1-Phosphatidylinositol 4-Kinase; Alpha-Globulins/chemistry; Animals; Cells, Cultured; Glycoproteins/metabolism; Golgi Apparatus/metabolism; Liver/metabolism; Male; Membrane Glycoproteins; Phosphotransferases/metabolism; Protein Precursors/chemistry; Rats; Rats, Sprague-Dawley; Subcellular Fractions/metabolism; Trypsin Inhibitor, Kunitz Soybean}},
language = {{eng}},
month = {{06}},
number = {{2}},
pages = {{54--147}},
publisher = {{Elsevier}},
series = {{Biochimica et Biophysica Acta}},
title = {{Cleavage of the alpha 1-microglobulin-bikunin precursor is localized to the Golgi apparatus of rat liver cells}},
url = {{http://dx.doi.org/10.1016/0304-4165(93)90058-G}},
doi = {{10.1016/0304-4165(93)90058-G}},
volume = {{1157}},
year = {{1993}},
}