Chloroplast ribosomal protein L-18 in Chlamydomonas reinhardtii is processed during ribosome assembly

✍ Scribed by Liu, Xiang-Qin ;Gillham, Nicholas W. ;Boynton, John E.

• Book ID: 104725144
• Publisher: Springer
• Year: 1988
• Tongue: English
• Weight: 692 KB
• Volume: 214
• Category: Article
• ISSN: 0026-8925
• DOI: 10.1007/bf00330499

✦ Synopsis

Chloroplast ribosomal protein L-18 is made in the cytoplasm as a precursor, imported into the chloroplast, and processed to the mature form in two steps. We report here that the intermediate produced following the first processing step associates specifically with a ribosomal complex migrating with the chloroplast ribosome large subunit peak in sucrose gradients, and is then processed into mature L-18. This processing event is slowed down in mutant cells deficient in synthesis of non-ribosomal proteins in the chloroplast. Thus the second processing step of L-18 occurs during ribosome assembly, depends on one or more nonribosomal proteins made in the chloroplast, and may be required for the maturation of the 50 S ribosome subunit. The mature L-18 protein shows extensive sequence homology at its amino-terminus to Escherichia coli ribosomal protein L27, which is located at the interface between 30 S and 50 S subunits and is involved in the formation of the peptidyl-tRNA binding site.