Bound Ribosomes of Pea Chloroplast Thylakoid Membranes: Location and Release in Vitro by High Salt, Puromycin, and RNase 1

AUTOR(ES)

Yamamoto, Taibo

RESUMO

The mode of attachment of 70S ribosomes to thylakoid membranes from pea leaves was studied by determining the proportion of the bound RNA which was released by various incubation conditions. The results supported a model in which several classes of bound ribosomes could be distinguished: (a) very tightly bound, not released by any conditions yet tested (20% of the total); (b) monomeric ribosomes attached by electrostatic interaction with the membranes (30 to 40% of the total) and released by high salt; and (c) polysomes, with some of the ribosomes attached by a combination of electrostatic interactions and insertion of the nascent polypeptide chain into the membrane. These required a combination of puromycin and high salt for release. Other (“hanging”) ribosomes of the polysomes were inferred to be attached through mRNA but not actually attached to the membranes directly; they could be released by RNase under low salt conditions, as well as by puromycin plus high salt.

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