Guanosine tetra- and pentaphosphate synthase activity in chloroplasts of a higher plant: association with 70S ribosomes and inhibition by tetracycline.

ABSTRACT: Chloroplasts possess bacterial-type systems for transcription and translation. On the basis of the identification of a Chlamydomonas reinhardtii gene encoding a RelA-SpoT homolog (RSH) that catalyzes the synthesis of guanosine tetra- or pentaphosphate [(p)ppGpp], we have previously suggested the operation of stringent control in the chloroplast genetic system. Although RSH genes have also been identified in several higher plants, the activities of the encoded enzymes and their mode of action in chloroplasts have remained uncharacterized. We have now characterized the intrinsic (p)ppGpp synthase activity of chloroplast extracts prepared from pea (Pisum sativum). Fractionation by ultracentrifugation suggested that the (p)ppGpp synthase activity of a translationally active chloroplast stromal

SUBMITTER: Kasai K 

PROVIDER: S-EPMC528801 | biostudies-literature | 2004

REPOSITORIES: biostudies-literature