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Propriétés des ribosomes et du RNA synthétisés par Escherichia coli cultivé en présence d'éthionine.
- Source :
- European Journal of Biochemistry; 1971, Vol. 20 Issue 4, p525-534, 10p
- Publication Year :
- 1971
-
Abstract
- Two isogenic derivatives of Escherichia coli K12: strains EA 1 (Met<superscript>-</superscript>, Biot<superscript>-</superscript>, RC<superscript>str</superscript> and EA 2 (Mei<superscript>-</superscript>, Biot<superscript>-</superscript>, RC<superscript>rel</superscript>) when grown in the presence of ethionine in place of methionine, synthesize ribosomes whose RNA is submethylated and whose proteins contain ethionine. Net ribosome synthesis in the presence of ethionine is greater in the RC<superscript>rel</superscript> strain than in the RC<superscript>str</superscript> strain. The precedinig paper describes results obtained with the latter strain. Here we present further studies carried out with the isogenic RC<superscript>rel</superscript> strain EA 2 As in the case of the RC<superscript>str</superscript> strain (previous paper) ribosomes synthesized by the RC<superscript>rel</superscript> strain grown in the presence of ethionine display defective association properties. A large fraction of these "ethionine" ribosomes is found as free subunits in crude extracts containing 10 mM Mg<superscript>+</superscript> prepared from strain EA 2 grown in an ethionine-containing medium. These free "ethionine" subunits have sedimentation coefficients of 28 S and 45 S approximately while the "ethionine" subunits found associated as 70 S particles in crude bacterial extracts sediment at 30 S and 50 S respectively. Both classes of "ethionine" subunits (free, and associated) can be methylated in vitro in the presence of S-adenosyl methionine with or without the addition of an external source of methylases (100000 x g supernatant of a homologous crude bacterial extract) The latter observation shows that the "ethionine" subunits contain bound methylases. These enzymes do not seem to be normal ribosomal proteins nor to be bound specifically to "ethionine" ribosomes since (a) they are removed by washing the "ethionine" ribosomes with 1 M NH<subscript>4</subscript>Cl, and (b) they are found bound to normal methionine ribosomes from which they are also removed by washing with 1 M NH<subscript>4</subscript>Cl. [ABSTRACT FROM AUTHOR]
- Subjects :
- RIBOSOMES
ESCHERICHIA coli
ORGANELLES
METHYLTRANSFERASES
ADENOSYLMETHIONINE
PROTEINS
Subjects
Details
- Language :
- English
- ISSN :
- 00142956
- Volume :
- 20
- Issue :
- 4
- Database :
- Complementary Index
- Journal :
- European Journal of Biochemistry
- Publication Type :
- Academic Journal
- Accession number :
- 12444094
- Full Text :
- https://doi.org/10.1111/j.1432-1033.1971.tb01423.x