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Complex formation between glutamyl‐tRNA synthetase and glutamyl‐ tRNA reductase during the tRNA‐dependent synthesis of 5‐aminolevulinic acid in Chlamydomonas reinhardtii
Author(s) -
Jahn Dieter
Publication year - 1992
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(92)81465-x
Subject(s) - chlamydomonas reinhardtii , transfer rna , biochemistry , chlamydomonas , chemistry , enzyme , biology , gene , rna , mutant
The formation of a stable complex between glutamyl‐tRNA synthetase and the first enzyme of chlorophyll biosynthesis glutamyl‐tRNA reductase was investigated in the green alga Chlamydomonas reinhardtii . Apparently homogenous enzymes, purified after previously established purification protocols were incubated in various combinations with ATP, glutamate, tRNA Glu and NADPH and formed complexes were isolated via glycerol gradient centrifugation. Stable complexes were detected only after the preincubation of glutamyl‐tRNA synthetase, glutamyl‐tRNA reductase with either glutamyl‐tRNA or free tRNA Glu , ATP and glutamate, indicating the obligatory requirement of aminoacylated tRNA Glu for complex formation. The further addition of NADPH resulting in the reduction of the tRNA‐bound glutamate to glutamate 1‐semialdehyde led to the dissociation of the complex. Once complexed to the two enzymes tRNA Glu was found to be partially protected from ribonuclease digestion. Escherichia coli , Bacillus subtilis and Synechocystis 6803 tRNA Glu were efficiently incorporated into the protein—RNA complex. The detected complexes provide the chloroplast with a potential channeling mechanism for Glu‐tRNA Glu into chlorophyll synthesis in order to compete with the chloroplastic protein synthesis machinery.