Rapid degradation of unassembled ribulose 1,5-bisphosphate carboxylase small subunits in chloroplasts

Abstract
A proteolytic mechanisms was detected in chloroplasts [of Chlamydomonas reinhardtii] that selectively and rapidly degrades the imported small subunit of ribulose 1,5-bisphosphate carboxylase when pools of the chloroplast-synthesized large subunit are depleted. This degradation system is constitutively present and appears to be responsible for precise stoichiometric accumulation of the 2 subsunits of the enzyme. Similar proteolytic mechanisms probably participate in regulating the accumulation of other photosynthetic proteins during chloroplast biogenesis.