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Muscle ribosome detachment factor
Author(s) -
Ionasescu Victor,
Braga Susana,
Kaeding Larry,
Rubenstein Peter,
Kalnitsky George,
Chatterjee Ranjit
Publication year - 1981
Publication title -
acta neurologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.967
H-Index - 95
eISSN - 1600-0404
pISSN - 0001-6314
DOI - 10.1111/j.1600-0404.1981.tb04393.x
Subject(s) - ribosome , leupeptin , differential centrifugation , microsome , biochemistry , centrifugation , sephadex , pepstatin , chemistry , proteolysis , biology , chromatography , protease , rna , in vitro , enzyme , gene
A protein that detaches ribosomes from rough microsomal membranes (“detachment factor”) (DF) was isolated from the cytosol fraction of rat and human muscle. The procedure of isolation included differential centrifugation, precipitation with ammonium sulfate and column chromatography with Sephadex G‐100. The protein which is not completely homogenous, has a molecular weight of 50,000–60,000 daltons, is heat labile and has an optimum pH at 7.4–7.6. The DF activity of the protein is inhibited by soybean trypsin inhibitor (73%), pepstatin (67%), and leupeptin (42%), although no proteolysis could be measured. The DF activity was tested on muscle samples (rough microsomal membranes) obtained from Duchenne muscular dystrophy (DMD) patients (7 cases) and normal controls (16 cases). The yield of membrane bound ribosomes (MBR) obtained from muscle samples of DMD patients by extraction with DF is 5‐fold higher than from muscle samples of normal controls. The difference in MBR yield is not related to the type of DF. Similar values for MBR were obtained with rat and human (normal and dystrophic) DF. Ribosomal protein synthesis (RPS) with ribosomes extracted by DF showed values similar to the RPS of detergent extracted ribosomes. Our findings suggest the observed increase in membrane bound ribosomes in DMD probably results from increased levels of mRNAs coding for membrane and secretory proteins such as collagen.