Expression and functional assembly into bacterial ribosomes of a nuclear-encoded chloroplast ribosomal protein with a long NH2-terminal extension

• Published in: FEBS letters 1991-08, Vol.288 (1-2), p.72-76
• Main Authors: Giese, Klaus, Subramanian, Alap R.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Base Sequence; Biological and medical sciences; Biological evolution; Chloroplast ribosome; Chloroplasts - metabolism; Chloroplast—bacterial hybrid ribosome; clongation factor Tu; COOH-terminal extension; CTE; EF-Tu; Endosymbiont hypothesis; Escherichia coli - metabolism; Fundamental and applied biological sciences. Psychology; Gene Expression - physiology; Genetics of eukaryotes. Biological and molecular evolution; LI3 protein expression; Macromolecular Substances; Molecular Sequence Data; NH2-terminal extension; NTE; PCR; Plants - genetics; Polymerase Chain Reaction; Polyribosomes - metabolism; r-protein; Recombinant Proteins - biosynthesis; ribosomal protein; Ribosomal Proteins - genetics; Ribosomal Proteins - metabolism; Ribosomes - metabolism; Ribosomes - physiology; SDS; sodium dodecyl sulfate
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/0014-5793(91)81005-S

Chloroplast ribosomal protein LI 3 is encoded in the plant nucleus and is considerably larger than its eubacterial homologue by having NH2- and COOH-terminal extensions with no homology to any known sequences (Phua et al., J. Biol. Chem. 264, 1968–1971, 1989). We made two gene constructs of LI3 cDNA using the polymerase chain reaction (PCR) and expressed them in Escherichia coli. Analysis of the ribosomes and polysomes from these calls, using an antiserum spelific to chloroplast LI3, shows that the expressed proteins are incorporated, in the presence of the homologous E. coli L13, into functional ribosomes which participate in protein synthesis (i.e. polysomes). Evidence is obtained that the large NH2-terminal extension probably lies on the surface of these ‘mosaic ribosomes’. This first report of the assembly into E. coli ribosomes of a nuclear-coded chloroplast ribosomal protein with terminal extensions thus suggests an extraordinary conservation in the function of eubactcrial type ribosomal proteins, despite the many changes in protein structure during their evolution inside a eukaryotic system.